From nobody Wed Apr 15 21:28:43 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 734B5C433FE for ; Mon, 21 Nov 2022 19:01:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230479AbiKUTBV (ORCPT ); Mon, 21 Nov 2022 14:01:21 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34038 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230419AbiKUTA6 (ORCPT ); Mon, 21 Nov 2022 14:00:58 -0500 Received: from mx.sberdevices.ru (mx.sberdevices.ru [45.89.227.171]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C7830CFEAD for ; Mon, 21 Nov 2022 11:00:54 -0800 (PST) Received: from s-lin-edge02.sberdevices.ru (localhost [127.0.0.1]) by mx.sberdevices.ru (Postfix) with ESMTP id CEA685FD0A; Mon, 21 Nov 2022 22:00:51 +0300 (MSK) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sberdevices.ru; s=mail; t=1669057251; bh=kumGGf0n9GsE8elc+YiswTIrEmu/kdjc+b63/oj/1bM=; h=From:To:Subject:Date:Message-ID:MIME-Version:Content-Type; b=NmwRG5yeHoXLB+0ePEEpvQuFTvnvB8StL9Sbv0T9oaC6Nq3FMdSW1DrwmoNLO08a5 OrXEpCTqlMyJBaFdUxvnAQsigL6Zh41v1w1+AJYxrLNo5Yi5aE/4bVOjuFZ41QHDdY 2aAqD6gBDGrW0RzoCyHItJ5OIIufnNdd9omWo1oG85t+xCAUsfhFbzj2Qq8TXpc3o+ mFNQTjtA+lOidObN8lkj0Phyz0+sxZJpXc013CQknoSgMJcXpxGIX5jyxqKuhtVpIN 6ww9dPQyDjnaA6Or1WFWF4AWqAH1mfvfRz5xyjTPKHueqagLa9f88sCfFfQ50nyeTF 3ullvV+1ZafsA== Received: from S-MS-EXCH01.sberdevices.ru (S-MS-EXCH01.sberdevices.ru [172.16.1.4]) by mx.sberdevices.ru (Postfix) with ESMTP; Mon, 21 Nov 2022 22:00:51 +0300 (MSK) From: Alexey Romanov To: , , , CC: , , , , Alexey Romanov Subject: [RFC PATCH v1 1/4] zram: introduce merge identical pages mechanism Date: Mon, 21 Nov 2022 22:00:17 +0300 Message-ID: <20221121190020.66548-2-avromanov@sberdevices.ru> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20221121190020.66548-1-avromanov@sberdevices.ru> References: <20221121190020.66548-1-avromanov@sberdevices.ru> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [172.16.1.6] X-ClientProxiedBy: S-MS-EXCH01.sberdevices.ru (172.16.1.4) To S-MS-EXCH01.sberdevices.ru (172.16.1.4) X-KSMG-Rule-ID: 4 X-KSMG-Message-Action: clean X-KSMG-AntiSpam-Status: not scanned, disabled by settings X-KSMG-AntiSpam-Interceptor-Info: not scanned X-KSMG-AntiPhishing: not scanned, disabled by settings X-KSMG-AntiVirus: Kaspersky Secure Mail Gateway, version 1.1.2.30, bases: 2022/11/21 16:41:00 #20594217 X-KSMG-AntiVirus-Status: Clean, skipped Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" zram maps each page (struct page) to a zsmalloc object that contains a compressed buffer of that page's data. This fact generates data redundancy: for example, two identical pages will be store in compressed form in zsmalloc allocator twice. This patch adds a mechanism to scan zram_table_entry array and frees all identical objects in zsmalloc allocator, leaving only one. All zram_table_entry elements which reference this freed objects now refer to the same, not freed, object. To implement this mechanism, we sequentially scan the zram_table_entry array, counting the hash from the contents of the compressed pages (zsmalloc objects) and enter the index of the object into the hash table (hlist_head). If the hash matches, we remove the identical zsmalloc (zs_free) objects and update the link rbtree. Also, we can't just call zs_free() function during zram_free_page(). Before calling this function we have to make sure that no one else refers to this zsmalloc object. To implement the mechanism for merging identical compressed pages (zsmalloc objects), a rbtree is needed. The tree node key is a reference to the zsmalloc object (handle), and the value is the number of references to this object (atomic counter). This is necessary for data consistency so that we do not zs_free the object referenced by any element of the zram_table_entry array. Signed-off-by: Alexey Romanov --- drivers/block/zram/zram_drv.c | 278 +++++++++++++++++++++++++++++++++- drivers/block/zram/zram_drv.h | 6 + 2 files changed, 283 insertions(+), 1 deletion(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index e290d6d97047..716c2f72805e 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -33,12 +33,15 @@ #include #include #include +#include +#include =20 #include "zram_drv.h" =20 static DEFINE_IDR(zram_index_idr); /* idr index must be protected */ static DEFINE_MUTEX(zram_index_mutex); +static DEFINE_MUTEX(zram_rbtree_mutex); =20 static int zram_major; static const char *default_compressor =3D CONFIG_ZRAM_DEF_COMP; @@ -57,6 +60,16 @@ static void zram_free_page(struct zram *zram, size_t ind= ex); static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec, u32 index, int offset, struct bio *bio); =20 +struct zram_rbtree_node { + struct rb_node node; + unsigned long key; + unsigned long cnt; +}; + +struct zram_hash_node { + unsigned long index; + struct hlist_node next; +}; =20 static int zram_slot_trylock(struct zram *zram, u32 index) { @@ -1283,6 +1296,247 @@ static DEVICE_ATTR_RO(bd_stat); #endif static DEVICE_ATTR_RO(debug_stat); =20 +static bool zram_rbtree_insert(struct rb_root *root, struct zram_rbtree_no= de *data) +{ + struct rb_node **new =3D &(root->rb_node), *parent =3D NULL; + struct zram_rbtree_node *this; + + while (*new) { + this =3D rb_entry(*new, struct zram_rbtree_node, node); + parent =3D *new; + if (data->key < this->key) + new =3D &((*new)->rb_left); + else if (data->key > this->key) + new =3D &((*new)->rb_right); + else + return false; + } + + rb_link_node(&data->node, parent, new); + rb_insert_color(&data->node, root); + return true; +} + +static struct zram_rbtree_node *zram_rbtree_search(struct rb_root *root, + unsigned long key) +{ + struct rb_node *node =3D root->rb_node; + struct zram_rbtree_node *data; + + while (node) { + data =3D rb_entry(node, struct zram_rbtree_node, node); + if (key < data->key) + node =3D node->rb_left; + else if (key > data->key) + node =3D node->rb_right; + else + return data; + } + + return NULL; +} + +static unsigned long zram_calc_hash(void *src, size_t len) +{ + return xxhash(src, len, 0); +} + +static int zram_cmp_obj_and_merge(struct zram *zram, struct hlist_head *ht= able, + size_t htable_size, size_t index) +{ + struct zram_rbtree_node *rb_node; + struct zram_hash_node *node; + unsigned long handle, cur_handle; + size_t obj_size; + char *src, *buf; + unsigned long hash; + int ret =3D 0; + + handle =3D zram_get_handle(zram, index); + if (!handle) + return ret; + + obj_size =3D zram_get_obj_size(zram, index); + buf =3D kmalloc(obj_size, GFP_KERNEL); + if (!buf) { + pr_err("Failed to allocate zs_map_object buffer\n"); + return -ENOMEM; + } + + src =3D zs_map_object(zram->mem_pool, handle, ZS_MM_RO); + memcpy(buf, src, obj_size); + zs_unmap_object(zram->mem_pool, handle); + hash =3D zram_calc_hash(buf, obj_size); + + mutex_lock(&zram_rbtree_mutex); + hlist_for_each_entry(node, &htable[hash % htable_size], next) { + int cmp; + + zram_slot_lock(zram, node->index); + + /* + * Page may change as the hash table is being formed, + * so the checks below are necessary. + */ + cur_handle =3D zram_get_handle(zram, node->index); + if (handle =3D=3D cur_handle || + obj_size !=3D zram_get_obj_size(zram, node->index)) { + zram_slot_unlock(zram, node->index); + continue; + } + + src =3D zs_map_object(zram->mem_pool, cur_handle, ZS_MM_RO); + cmp =3D memcmp(buf, src, obj_size); + zs_unmap_object(zram->mem_pool, cur_handle); + + if (!cmp) { + rb_node =3D zram_rbtree_search(&zram->sph_rbtree, handle); + + /* + * This check is necessary in order not to zs_free an object + * that someone already refers to. This situation is possible + * when with repeated calls to zram_do_scan(). For example: + * + * [slot0] [slot1] [slot2] [slot3] [slot4] + * [obj0] [obj1] [obj2] [obj3] [obj4] + * + * Let's imagine that obj2 and obj3 are equal, and we called + * zram_do_scan() function: + * + * [slot0] [slot1] [slot2] [slot3] [slot4] + * [obj0] [obj1] [obj2] [obj2] [obj4] + * + * Now, slot2 and slot3 refers to obj2 zsmalloc object. + * Time passed, now slot0 refres to obj0_n, which is equal + * to obj2: + * + * [slot0] [slot1] [slot2] [slot3] [slot4] + * [obj0_n] [obj1] [obj2] [obj2] [obj4] + * + * Now we call zram_do_scan() function again. We get to slot2, + * and we understand that obj2 and obj0_n hashes are the same. We + * try to zs_free(obj2), but slot3 also already refers to it. + * + * This is not correct! + */ + if (unlikely(rb_node)) + if (rb_node->cnt > 1) { + zram_slot_unlock(zram, node->index); + continue; + } + + zram_set_handle(zram, index, cur_handle); + zs_free(zram->mem_pool, handle); + + rb_node =3D zram_rbtree_search(&zram->sph_rbtree, cur_handle); + + if (!rb_node) { + rb_node =3D kzalloc(sizeof(struct zram_rbtree_node), + GFP_KERNEL); + if (!rb_node) { + pr_err("Failed to allocate rb_node\n"); + ret =3D -ENOMEM; + zram_slot_unlock(zram, node->index); + mutex_unlock(&zram_rbtree_mutex); + goto merged_or_err; + } + + rb_node->key =3D cur_handle; + /* Two slots refers to an zsmalloc object with cur_handle key */ + rb_node->cnt =3D 2; + zram_rbtree_insert(&zram->sph_rbtree, rb_node); + } else { + rb_node->cnt++; + } + + atomic64_sub(obj_size, &zram->stats.compr_data_size); + zram_set_flag(zram, index, ZRAM_MERGED); + zram_set_flag(zram, node->index, ZRAM_MERGED); + + zram_slot_unlock(zram, node->index); + mutex_unlock(&zram_rbtree_mutex); + goto merged_or_err; + } + + zram_slot_unlock(zram, node->index); + } + + mutex_unlock(&zram_rbtree_mutex); + + node =3D kmalloc(sizeof(struct zram_hash_node), GFP_KERNEL); + if (!node) { + ret =3D -ENOMEM; + goto merged_or_err; + } + + node->index =3D index; + hlist_add_head(&node->next, &htable[hash % htable_size]); + +merged_or_err: + kfree(buf); + return ret; +} + +static void zram_free_htable_entries(struct hlist_head *htable, + size_t htable_size) +{ + struct hlist_node *n; + struct zram_hash_node *node; + + hlist_for_each_entry_safe(node, n, htable, next) { + hlist_del(&node->next); + kfree(node); + } +} + +static int zram_do_scan(struct zram *zram) +{ + size_t num_pages =3D zram->disksize >> PAGE_SHIFT; + size_t htable_size =3D num_pages; + size_t index; + struct hlist_head *htable; + int i, ret =3D 0; + + htable =3D vzalloc(htable_size * sizeof(struct hlist_head)); + if (!htable) { + pr_err("Failed to allocate hash table\n"); + return -ENOMEM; + } + + for (i =3D 0; i < htable_size; i++) + INIT_HLIST_HEAD(&htable[i]); + + for (index =3D 0; index < num_pages; index++) { + zram_slot_lock(zram, index); + + if (!zram_allocated(zram, index)) { + zram_slot_unlock(zram, index); + continue; + } + + if (zram_test_flag(zram, index, ZRAM_UNDER_WB) || + zram_test_flag(zram, index, ZRAM_WB) || + zram_test_flag(zram, index, ZRAM_SAME)) { + zram_slot_unlock(zram, index); + continue; + } + + /* Ignore pages that have been recompressed */ + if (zram_get_priority(zram, index) !=3D 0) + continue; + + ret =3D zram_cmp_obj_and_merge(zram, htable, htable_size, index); + zram_slot_unlock(zram, index); + if (ret !=3D 0) + goto out; + } + +out: + zram_free_htable_entries(htable, htable_size); + vfree(htable); + return ret; +} + static void zram_meta_free(struct zram *zram, u64 disksize) { size_t num_pages =3D disksize >> PAGE_SHIFT; @@ -1324,6 +1578,7 @@ static bool zram_meta_alloc(struct zram *zram, u64 di= sksize) static void zram_free_page(struct zram *zram, size_t index) { unsigned long handle; + struct zram_rbtree_node *node; =20 #ifdef CONFIG_ZRAM_MEMORY_TRACKING zram->table[index].ac_time =3D 0; @@ -1361,7 +1616,26 @@ static void zram_free_page(struct zram *zram, size_t= index) if (!handle) return; =20 - zs_free(zram->mem_pool, handle); + if (zram_test_flag(zram, index, ZRAM_MERGED)) { + zram_clear_flag(zram, index, ZRAM_MERGED); + mutex_lock(&zram_rbtree_mutex); + + node =3D zram_rbtree_search(&zram->sph_rbtree, handle); + BUG_ON(!node); + + node->cnt--; + if (node->cnt =3D=3D 0) { + rb_erase(&node->node, &zram->sph_rbtree); + mutex_unlock(&zram_rbtree_mutex); + + zs_free(zram->mem_pool, handle); + kfree(node); + } else { + mutex_unlock(&zram_rbtree_mutex); + } + } else { + zs_free(zram->mem_pool, handle); + } =20 atomic64_sub(zram_get_obj_size(zram, index), &zram->stats.compr_data_size); @@ -2421,6 +2695,8 @@ static int zram_add(void) =20 comp_algorithm_set(zram, ZRAM_PRIMARY_COMP, default_compressor); =20 + zram->sph_rbtree =3D RB_ROOT; + zram_debugfs_register(zram); pr_info("Added device: %s\n", zram->disk->disk_name); return device_id; diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h index c5254626f051..4a7151c94523 100644 --- a/drivers/block/zram/zram_drv.h +++ b/drivers/block/zram/zram_drv.h @@ -56,6 +56,7 @@ enum zram_pageflags { =20 ZRAM_COMP_PRIORITY_BIT1, /* First bit of comp priority index */ ZRAM_COMP_PRIORITY_BIT2, /* Second bit of comp priority index */ + ZRAM_MERGED, /* page was merged */ =20 __NR_ZRAM_PAGEFLAGS, }; @@ -140,5 +141,10 @@ struct zram { #ifdef CONFIG_ZRAM_MEMORY_TRACKING struct dentry *debugfs_dir; #endif + /* + * This is same pages handle's rb tree, where the key is a handle + * to same pages and the value is a link counter + */ + struct rb_root sph_rbtree; }; #endif --=20 2.25.1 From nobody Wed Apr 15 21:28:43 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C551EC433FE for ; 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Mon, 21 Nov 2022 22:00:52 +0300 (MSK) From: Alexey Romanov To: , , , CC: , , , , Alexey Romanov Subject: [RFC PATCH v1 2/4] zram: add merge sysfs knob Date: Mon, 21 Nov 2022 22:00:18 +0300 Message-ID: <20221121190020.66548-3-avromanov@sberdevices.ru> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20221121190020.66548-1-avromanov@sberdevices.ru> References: <20221121190020.66548-1-avromanov@sberdevices.ru> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [172.16.1.6] X-ClientProxiedBy: S-MS-EXCH01.sberdevices.ru (172.16.1.4) To S-MS-EXCH01.sberdevices.ru (172.16.1.4) X-KSMG-Rule-ID: 4 X-KSMG-Message-Action: clean X-KSMG-AntiSpam-Status: not scanned, disabled by settings X-KSMG-AntiSpam-Interceptor-Info: not scanned X-KSMG-AntiPhishing: not scanned, disabled by settings X-KSMG-AntiVirus: Kaspersky Secure Mail Gateway, version 1.1.2.30, bases: 2022/11/21 16:41:00 #20594217 X-KSMG-AntiVirus-Status: Clean, skipped Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Allow zram to merge identical pages into signle one: echo 1 > /sys/block/zramX/merge Signed-off-by: Alexey Romanov --- drivers/block/zram/zram_drv.c | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 716c2f72805e..1dae3564cabd 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -1197,6 +1197,30 @@ static ssize_t compact_store(struct device *dev, return len; } =20 +static int zram_do_scan(struct zram *zram); + +static ssize_t merge_store(struct device *dev, + struct device_attribute *attr, const char *buf, size_t len) +{ + struct zram *zram =3D dev_to_zram(dev); + int ret; + + down_read(&zram->init_lock); + if (!init_done(zram)) { + up_read(&zram->init_lock); + return -EINVAL; + } + + ret =3D zram_do_scan(zram); + if (ret !=3D 0) { + up_read(&zram->init_lock); + return -ENOMEM; + } + + up_read(&zram->init_lock); + return len; +} + static ssize_t io_stat_show(struct device *dev, struct device_attribute *attr, char *buf) { @@ -2569,6 +2593,7 @@ static const struct block_device_operations zram_devo= ps =3D { }; =20 static DEVICE_ATTR_WO(compact); +static DEVICE_ATTR_WO(merge); static DEVICE_ATTR_RW(disksize); static DEVICE_ATTR_RO(initstate); static DEVICE_ATTR_WO(reset); @@ -2609,6 +2634,7 @@ static struct attribute *zram_disk_attrs[] =3D { #ifdef CONFIG_ZRAM_WRITEBACK &dev_attr_bd_stat.attr, #endif + &dev_attr_merge.attr, &dev_attr_debug_stat.attr, #ifdef CONFIG_ZRAM_MULTI_COMP &dev_attr_recomp_algorithm.attr, --=20 2.25.1 From nobody Wed Apr 15 21:28:43 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D31E8C433FE for ; Mon, 21 Nov 2022 19:01:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229865AbiKUTBJ (ORCPT ); Mon, 21 Nov 2022 14:01:09 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34036 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230416AbiKUTA6 (ORCPT ); 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Mon, 21 Nov 2022 22:00:53 +0300 (MSK) From: Alexey Romanov To: , , , CC: , , , , Alexey Romanov Subject: [RFC PATCH v1 3/4] zram: add pages_merged counter to mm_stat Date: Mon, 21 Nov 2022 22:00:19 +0300 Message-ID: <20221121190020.66548-4-avromanov@sberdevices.ru> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20221121190020.66548-1-avromanov@sberdevices.ru> References: <20221121190020.66548-1-avromanov@sberdevices.ru> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [172.16.1.6] X-ClientProxiedBy: S-MS-EXCH01.sberdevices.ru (172.16.1.4) To S-MS-EXCH01.sberdevices.ru (172.16.1.4) X-KSMG-Rule-ID: 4 X-KSMG-Message-Action: clean X-KSMG-AntiSpam-Status: not scanned, disabled by settings X-KSMG-AntiSpam-Interceptor-Info: not scanned X-KSMG-AntiPhishing: not scanned, disabled by settings X-KSMG-AntiVirus: Kaspersky Secure Mail Gateway, version 1.1.2.30, bases: 2022/11/21 16:41:00 #20594217 X-KSMG-AntiVirus-Status: Clean, skipped Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" This counter shows how many identical compressed pages have been processed by zram so far. Signed-off-by: Alexey Romanov --- Documentation/admin-guide/blockdev/zram.rst | 2 ++ drivers/block/zram/zram_drv.c | 8 ++++++-- drivers/block/zram/zram_drv.h | 1 + 3 files changed, 9 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/blockdev/zram.rst b/Documentation/ad= min-guide/blockdev/zram.rst index e4551579cb12..a1dd202efca1 100644 --- a/Documentation/admin-guide/blockdev/zram.rst +++ b/Documentation/admin-guide/blockdev/zram.rst @@ -209,6 +209,7 @@ compact WO trigger memory compaction debug_stat RO this file is used for zram debugging purposes backing_dev RW set up backend storage for zram to write out idle WO mark allocated slot as idle +merge WO trigger merge identical pages =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D= =3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D =20 =20 @@ -267,6 +268,7 @@ line of text and contains the following stats separated= by whitespace: pages_compacted the number of pages freed during compaction huge_pages the number of incompressible pages huge_pages_since the number of incompressible pages since zram set up + pages_merged the number of identical pages merged into single one =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D =20 File /sys/block/zram/bd_stat diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 1dae3564cabd..7a267b37e5db 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -1260,7 +1260,7 @@ static ssize_t mm_stat_show(struct device *dev, max_used =3D atomic_long_read(&zram->stats.max_used_pages); =20 ret =3D scnprintf(buf, PAGE_SIZE, - "%8llu %8llu %8llu %8lu %8ld %8llu %8lu %8llu %8llu\n", + "%8llu %8llu %8llu %8lu %8ld %8llu %8lu %8llu %8llu %8llu\n", orig_size << PAGE_SHIFT, (u64)atomic64_read(&zram->stats.compr_data_size), mem_used << PAGE_SHIFT, @@ -1269,7 +1269,8 @@ static ssize_t mm_stat_show(struct device *dev, (u64)atomic64_read(&zram->stats.same_pages), atomic_long_read(&pool_stats.pages_compacted), (u64)atomic64_read(&zram->stats.huge_pages), - (u64)atomic64_read(&zram->stats.huge_pages_since)); + (u64)atomic64_read(&zram->stats.huge_pages_since), + (u64)atomic64_read(&zram->stats.pages_merged)); up_read(&zram->init_lock); =20 return ret; @@ -1473,6 +1474,7 @@ static int zram_cmp_obj_and_merge(struct zram *zram, = struct hlist_head *htable, rb_node->cnt++; } =20 + atomic64_inc(&zram->stats.pages_merged); atomic64_sub(obj_size, &zram->stats.compr_data_size); zram_set_flag(zram, index, ZRAM_MERGED); zram_set_flag(zram, node->index, ZRAM_MERGED); @@ -1657,6 +1659,8 @@ static void zram_free_page(struct zram *zram, size_t = index) } else { mutex_unlock(&zram_rbtree_mutex); } + + atomic64_dec(&zram->stats.pages_merged); } else { zs_free(zram->mem_pool, handle); } diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h index 4a7151c94523..2afdbf76a1aa 100644 --- a/drivers/block/zram/zram_drv.h +++ b/drivers/block/zram/zram_drv.h @@ -88,6 +88,7 @@ struct zram_stats { atomic_long_t max_used_pages; /* no. of maximum pages stored */ atomic64_t writestall; /* no. of write slow paths */ atomic64_t miss_free; /* no. of missed free */ + atomic64_t pages_merged; /* no. of pages, which merged into single one */ #ifdef CONFIG_ZRAM_WRITEBACK atomic64_t bd_count; /* no. of pages in backing device */ atomic64_t bd_reads; /* no. of reads from backing device */ --=20 2.25.1 From nobody Wed Apr 15 21:28:43 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3885AC4332F for ; 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Mon, 21 Nov 2022 22:00:54 +0300 (MSK) From: Alexey Romanov To: , , , CC: , , , , Alexey Romanov Subject: [RFC PATCH v1 4/4] zram: recompression: add ZRAM_MERGED check Date: Mon, 21 Nov 2022 22:00:20 +0300 Message-ID: <20221121190020.66548-5-avromanov@sberdevices.ru> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20221121190020.66548-1-avromanov@sberdevices.ru> References: <20221121190020.66548-1-avromanov@sberdevices.ru> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Originating-IP: [172.16.1.6] X-ClientProxiedBy: S-MS-EXCH01.sberdevices.ru (172.16.1.4) To S-MS-EXCH01.sberdevices.ru (172.16.1.4) X-KSMG-Rule-ID: 4 X-KSMG-Message-Action: clean X-KSMG-AntiSpam-Status: not scanned, disabled by settings X-KSMG-AntiSpam-Interceptor-Info: not scanned X-KSMG-AntiPhishing: not scanned, disabled by settings X-KSMG-AntiVirus: Kaspersky Secure Mail Gateway, version 1.1.2.30, bases: 2022/11/21 16:41:00 #20594217 X-KSMG-AntiVirus-Status: Clean, skipped Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" It is not possible to recompress merged pages in the current implementation. Although, in the future it is possible to add support for recompression of merged pages. Signed-off-by: Alexey Romanov --- drivers/block/zram/zram_drv.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 7a267b37e5db..07661283ea15 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -2211,7 +2211,8 @@ static ssize_t recompress_store(struct device *dev, if (zram_test_flag(zram, index, ZRAM_WB) || zram_test_flag(zram, index, ZRAM_UNDER_WB) || zram_test_flag(zram, index, ZRAM_SAME) || - zram_test_flag(zram, index, ZRAM_INCOMPRESSIBLE)) + zram_test_flag(zram, index, ZRAM_INCOMPRESSIBLE) || + zram_test_flag(zram, index, ZRAM_MERGED)) goto next; =20 err =3D zram_recompress(zram, index, page, threshold, --=20 2.25.1