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bh=MtcLz3HoOuMb7dWaVW/7n137qzfJKsmUGSn1VyrRD58=; b=SjfxJleEp1JDj4xy2dkfdIf7LPhgK3JA22+/142axIunnsYt+xImBNteYUeQfLo7dv2hRg y/sRVzi1Y1/brnQGamRpkup8CPPjwPpLIeqgwwFFF55+TslEBBJkceAoPQFnQNXrdgkpPO qd2OenIAz4GVsqULZYRrUBzlGJVaHHM= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1752243058; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=MtcLz3HoOuMb7dWaVW/7n137qzfJKsmUGSn1VyrRD58=; b=fg/AZulPxsJ4R8duTEe1wKZT3ByQIu4/u2JvKLxuieeFCMbH5bXE2cqeYe1FhRs2OtjJ4h O8FtIRhqwwUYKTDA== From: Fabiano Rosas To: qemu-devel@nongnu.org Cc: Peter Xu , Yanfei Xu Subject: [PULL 11/26] migration/postcopy: Avoid clearing dirty bitmap for postcopy too Date: Fri, 11 Jul 2025 11:10:16 -0300 Message-Id: <20250711141031.423-12-farosas@suse.de> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20250711141031.423-1-farosas@suse.de> References: <20250711141031.423-1-farosas@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Spamd-Result: default: False [-2.80 / 50.00]; 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charset="utf-8" From: Peter Xu This is a follow up on the other commit "migration/ram: avoid to do log clear in the last round" but for postcopy. https://lore.kernel.org/r/20250514115827.3216082-1-yanfei.xu@bytedance.com I can observe more than 10% reduction of average page fault latency during postcopy phase with this optimization: Before: 268.00us (+-1.87%) After: 232.67us (+-2.01%) The test was done with a 16GB VM with 80 vCPUs, running a workload that busy random writes to 13GB memory. Cc: Yanfei Xu Reviewed-by: Fabiano Rosas Link: https://lore.kernel.org/r/20250613140801.474264-12-peterx@redhat.com Signed-off-by: Peter Xu Signed-off-by: Fabiano Rosas --- migration/ram.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/migration/ram.c b/migration/ram.c index e4871b4c17..7208bc114f 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -835,8 +835,10 @@ static inline bool migration_bitmap_clear_dirty(RAMSta= te *rs, * protections isn't needed as we know there will be either (1) no * further writes if migration will complete, or (2) migration fails * at last then tracking isn't needed either. + * + * Do the same for postcopy due to the same reason. */ - if (!rs->last_stage) { + if (!rs->last_stage && !migration_in_postcopy()) { /* * Clear dirty bitmap if needed. This _must_ be called before we * send any of the page in the chunk because we need to make sure --=20 2.35.3