mm/swapfile.c | 86 ++++++++++++++++++++++++++++++++--------------------------- 1 file changed, 47 insertions(+), 39 deletions(-)
This the alloc_swap_scan_list() will scan the whole list or the first
cluster.
This reduces the repeat patterns of isolating a cluster then scanning
that cluster. As a result, cluster_alloc_swap_entry() is shorter and shallower.
No functional change.
Signed-off-by: Chris Li <chrisl@kernel.org>
---
This patch goes on top of Kairui's swap improve cluster scan series:
https://lore.kernel.org/linux-mm/20250806161748.76651-1-ryncsn@gmail.com/
---
Changes in v2:
- Adjust change base on Andrew's feedback on int type and break out of
loop.
- Link to v1: https://lore.kernel.org/r/20250806-swap-scan-list-v1-1-a5fe2d9340a2@kernel.org
---
mm/swapfile.c | 86 ++++++++++++++++++++++++++++++++---------------------------
1 file changed, 47 insertions(+), 39 deletions(-)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 4a0cf4fb348d..f26678d68874 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -820,6 +820,29 @@ static unsigned int alloc_swap_scan_cluster(struct swap_info_struct *si,
return found;
}
+static unsigned int alloc_swap_scan_list(struct swap_info_struct *si,
+ struct list_head *list,
+ unsigned int order,
+ unsigned char usage,
+ bool scan_all)
+{
+ unsigned int found = SWAP_ENTRY_INVALID;
+
+ do {
+ struct swap_cluster_info *ci = isolate_lock_cluster(si, list);
+ unsigned long offset;
+
+ if (!ci)
+ break;
+ offset = cluster_offset(si, ci);
+ found = alloc_swap_scan_cluster(si, ci, offset, order, usage);
+ if (found)
+ break;
+ } while (scan_all);
+
+ return found;
+}
+
static void swap_reclaim_full_clusters(struct swap_info_struct *si, bool force)
{
long to_scan = 1;
@@ -913,32 +936,24 @@ static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, int o
* to spread out the writes.
*/
if (si->flags & SWP_PAGE_DISCARD) {
- ci = isolate_lock_cluster(si, &si->free_clusters);
- if (ci) {
- found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
- order, usage);
- if (found)
- goto done;
- }
+ found = alloc_swap_scan_list(si, &si->free_clusters, order, usage,
+ false);
+ if (found)
+ goto done;
}
if (order < PMD_ORDER) {
- while ((ci = isolate_lock_cluster(si, &si->nonfull_clusters[order]))) {
- found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
- order, usage);
- if (found)
- goto done;
- }
+ found = alloc_swap_scan_list(si, &si->nonfull_clusters[order],
+ order, usage, 0);
+ if (found)
+ goto done;
}
if (!(si->flags & SWP_PAGE_DISCARD)) {
- ci = isolate_lock_cluster(si, &si->free_clusters);
- if (ci) {
- found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
- order, usage);
- if (found)
- goto done;
- }
+ found = alloc_swap_scan_list(si, &si->free_clusters, order, usage,
+ false);
+ if (found)
+ goto done;
}
/* Try reclaim full clusters if free and nonfull lists are drained */
@@ -952,13 +967,10 @@ static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, int o
* failure is not critical. Scanning one cluster still
* keeps the list rotated and reclaimed (for HAS_CACHE).
*/
- ci = isolate_lock_cluster(si, &si->frag_clusters[order]);
- if (ci) {
- found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
- order, usage);
- if (found)
- goto done;
- }
+ found = alloc_swap_scan_list(si, &si->frag_clusters[order], order,
+ usage, true);
+ if (found)
+ goto done;
}
/*
@@ -977,19 +989,15 @@ static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, int o
* Clusters here have at least one usable slots and can't fail order 0
* allocation, but reclaim may drop si->lock and race with another user.
*/
- while ((ci = isolate_lock_cluster(si, &si->frag_clusters[o]))) {
- found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
- 0, usage);
- if (found)
- goto done;
- }
+ found = alloc_swap_scan_list(si, &si->frag_clusters[o],
+ 0, usage, true);
+ if (found)
+ goto done;
- while ((ci = isolate_lock_cluster(si, &si->nonfull_clusters[o]))) {
- found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
- 0, usage);
- if (found)
- goto done;
- }
+ found = alloc_swap_scan_list(si, &si->nonfull_clusters[o],
+ 0, usage, true);
+ if (found)
+ goto done;
}
done:
if (!(si->flags & SWP_SOLIDSTATE))
---
base-commit: f89484324d5876ee10765fa61da0332899fa1a6a
change-id: 20250806-swap-scan-list-2b89e3424b0a
Best regards,
--
Chris Li <chrisl@kernel.org>On Fri, Aug 8, 2025 at 3:48 PM Chris Li <chrisl@kernel.org> wrote:
>
> This the alloc_swap_scan_list() will scan the whole list or the first
> cluster.
Hi Chris,
This sentence reads strange to me, but English is not my native
language so I'm not very sure about it.
>
> This reduces the repeat patterns of isolating a cluster then scanning
> that cluster. As a result, cluster_alloc_swap_entry() is shorter and shallower.
>
> No functional change.
>
> Signed-off-by: Chris Li <chrisl@kernel.org>
> ---
> This patch goes on top of Kairui's swap improve cluster scan series:
> https://lore.kernel.org/linux-mm/20250806161748.76651-1-ryncsn@gmail.com/
> ---
> Changes in v2:
> - Adjust change base on Andrew's feedback on int type and break out of
> loop.
> - Link to v1: https://lore.kernel.org/r/20250806-swap-scan-list-v1-1-a5fe2d9340a2@kernel.org
> ---
> mm/swapfile.c | 86 ++++++++++++++++++++++++++++++++---------------------------
> 1 file changed, 47 insertions(+), 39 deletions(-)
>
> diff --git a/mm/swapfile.c b/mm/swapfile.c
> index 4a0cf4fb348d..f26678d68874 100644
> --- a/mm/swapfile.c
> +++ b/mm/swapfile.c
> @@ -820,6 +820,29 @@ static unsigned int alloc_swap_scan_cluster(struct swap_info_struct *si,
> return found;
> }
>
> +static unsigned int alloc_swap_scan_list(struct swap_info_struct *si,
> + struct list_head *list,
> + unsigned int order,
> + unsigned char usage,
> + bool scan_all)
> +{
> + unsigned int found = SWAP_ENTRY_INVALID;
> +
> + do {
> + struct swap_cluster_info *ci = isolate_lock_cluster(si, list);
> + unsigned long offset;
> +
> + if (!ci)
> + break;
> + offset = cluster_offset(si, ci);
> + found = alloc_swap_scan_cluster(si, ci, offset, order, usage);
> + if (found)
> + break;
> + } while (scan_all);
> +
> + return found;
> +}
> +
> static void swap_reclaim_full_clusters(struct swap_info_struct *si, bool force)
> {
> long to_scan = 1;
> @@ -913,32 +936,24 @@ static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, int o
> * to spread out the writes.
> */
> if (si->flags & SWP_PAGE_DISCARD) {
> - ci = isolate_lock_cluster(si, &si->free_clusters);
> - if (ci) {
> - found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
> - order, usage);
> - if (found)
> - goto done;
> - }
> + found = alloc_swap_scan_list(si, &si->free_clusters, order, usage,
> + false);
> + if (found)
> + goto done;
> }
>
> if (order < PMD_ORDER) {
> - while ((ci = isolate_lock_cluster(si, &si->nonfull_clusters[order]))) {
> - found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
> - order, usage);
> - if (found)
> - goto done;
> - }
> + found = alloc_swap_scan_list(si, &si->nonfull_clusters[order],
> + order, usage, 0);
All other alloc_swap_scan_list calls use `false`/`true` but this one
uses `0` for `scan_all`.
And it should be `true`, right?
> + if (found)
> + goto done;
> }
>
> if (!(si->flags & SWP_PAGE_DISCARD)) {
> - ci = isolate_lock_cluster(si, &si->free_clusters);
> - if (ci) {
> - found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
> - order, usage);
> - if (found)
> - goto done;
> - }
> + found = alloc_swap_scan_list(si, &si->free_clusters, order, usage,
> + false);
> + if (found)
> + goto done;
> }
>
> /* Try reclaim full clusters if free and nonfull lists are drained */
> @@ -952,13 +967,10 @@ static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, int o
> * failure is not critical. Scanning one cluster still
> * keeps the list rotated and reclaimed (for HAS_CACHE).
> */
> - ci = isolate_lock_cluster(si, &si->frag_clusters[order]);
> - if (ci) {
> - found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
> - order, usage);
> - if (found)
> - goto done;
> - }
> + found = alloc_swap_scan_list(si, &si->frag_clusters[order], order,
> + usage, true);
And it should be `false` here.
> + if (found)
> + goto done;
> }
>
> /*
> @@ -977,19 +989,15 @@ static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, int o
> * Clusters here have at least one usable slots and can't fail order 0
> * allocation, but reclaim may drop si->lock and race with another user.
> */
> - while ((ci = isolate_lock_cluster(si, &si->frag_clusters[o]))) {
> - found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
> - 0, usage);
> - if (found)
> - goto done;
> - }
> + found = alloc_swap_scan_list(si, &si->frag_clusters[o],
> + 0, usage, true);
> + if (found)
> + goto done;
>
> - while ((ci = isolate_lock_cluster(si, &si->nonfull_clusters[o]))) {
> - found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
> - 0, usage);
> - if (found)
> - goto done;
> - }
> + found = alloc_swap_scan_list(si, &si->nonfull_clusters[o],
> + 0, usage, true);
> + if (found)
> + goto done;
> }
> done:
> if (!(si->flags & SWP_SOLIDSTATE))
>
> ---
> base-commit: f89484324d5876ee10765fa61da0332899fa1a6a
> change-id: 20250806-swap-scan-list-2b89e3424b0a
>
> Best regards,
> --
> Chris Li <chrisl@kernel.org>
>
This makes the code much cleaner, thanks!
On Fri, Aug 8, 2025 at 12:52 PM Kairui Song <ryncsn@gmail.com> wrote:
>
> On Fri, Aug 8, 2025 at 3:48 PM Chris Li <chrisl@kernel.org> wrote:
> >
> > This the alloc_swap_scan_list() will scan the whole list or the first
> > cluster.
>
> Hi Chris,
>
> This sentence reads strange to me, but English is not my native
> language so I'm not very sure about it.
Ack, my bad, let me rephrase it.
>
> >
> > This reduces the repeat patterns of isolating a cluster then scanning
> > that cluster. As a result, cluster_alloc_swap_entry() is shorter and shallower.
> >
> > No functional change.
> >
> > Signed-off-by: Chris Li <chrisl@kernel.org>
> > ---
> > This patch goes on top of Kairui's swap improve cluster scan series:
> > https://lore.kernel.org/linux-mm/20250806161748.76651-1-ryncsn@gmail.com/
> > ---
> > Changes in v2:
> > - Adjust change base on Andrew's feedback on int type and break out of
> > loop.
> > - Link to v1: https://lore.kernel.org/r/20250806-swap-scan-list-v1-1-a5fe2d9340a2@kernel.org
> > ---
> > mm/swapfile.c | 86 ++++++++++++++++++++++++++++++++---------------------------
> > 1 file changed, 47 insertions(+), 39 deletions(-)
> >
> > diff --git a/mm/swapfile.c b/mm/swapfile.c
> > index 4a0cf4fb348d..f26678d68874 100644
> > --- a/mm/swapfile.c
> > +++ b/mm/swapfile.c
> > @@ -820,6 +820,29 @@ static unsigned int alloc_swap_scan_cluster(struct swap_info_struct *si,
> > return found;
> > }
> >
> > +static unsigned int alloc_swap_scan_list(struct swap_info_struct *si,
> > + struct list_head *list,
> > + unsigned int order,
> > + unsigned char usage,
> > + bool scan_all)
> > +{
> > + unsigned int found = SWAP_ENTRY_INVALID;
> > +
> > + do {
> > + struct swap_cluster_info *ci = isolate_lock_cluster(si, list);
> > + unsigned long offset;
> > +
> > + if (!ci)
> > + break;
> > + offset = cluster_offset(si, ci);
> > + found = alloc_swap_scan_cluster(si, ci, offset, order, usage);
> > + if (found)
> > + break;
> > + } while (scan_all);
> > +
> > + return found;
> > +}
> > +
> > static void swap_reclaim_full_clusters(struct swap_info_struct *si, bool force)
> > {
> > long to_scan = 1;
> > @@ -913,32 +936,24 @@ static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, int o
> > * to spread out the writes.
> > */
> > if (si->flags & SWP_PAGE_DISCARD) {
> > - ci = isolate_lock_cluster(si, &si->free_clusters);
> > - if (ci) {
> > - found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
> > - order, usage);
> > - if (found)
> > - goto done;
> > - }
> > + found = alloc_swap_scan_list(si, &si->free_clusters, order, usage,
> > + false);
> > + if (found)
> > + goto done;
> > }
> >
> > if (order < PMD_ORDER) {
> > - while ((ci = isolate_lock_cluster(si, &si->nonfull_clusters[order]))) {
> > - found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
> > - order, usage);
> > - if (found)
> > - goto done;
> > - }
> > + found = alloc_swap_scan_list(si, &si->nonfull_clusters[order],
> > + order, usage, 0);
>
> All other alloc_swap_scan_list calls use `false`/`true` but this one
> uses `0` for `scan_all`.
> And it should be `true`, right?
Yes, good catch. Will send out a V3.
>
> > + if (found)
> > + goto done;
> > }
> >
> > if (!(si->flags & SWP_PAGE_DISCARD)) {
> > - ci = isolate_lock_cluster(si, &si->free_clusters);
> > - if (ci) {
> > - found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
> > - order, usage);
> > - if (found)
> > - goto done;
> > - }
> > + found = alloc_swap_scan_list(si, &si->free_clusters, order, usage,
> > + false);
> > + if (found)
> > + goto done;
> > }
> >
> > /* Try reclaim full clusters if free and nonfull lists are drained */
> > @@ -952,13 +967,10 @@ static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, int o
> > * failure is not critical. Scanning one cluster still
> > * keeps the list rotated and reclaimed (for HAS_CACHE).
> > */
> > - ci = isolate_lock_cluster(si, &si->frag_clusters[order]);
> > - if (ci) {
> > - found = alloc_swap_scan_cluster(si, ci, cluster_offset(si, ci),
> > - order, usage);
> > - if (found)
> > - goto done;
> > - }
> > + found = alloc_swap_scan_list(si, &si->frag_clusters[order], order,
> > + usage, true);
>
> And it should be `false` here.
Ack.
Chris
On Sat, 9 Aug 2025 03:51:48 +0800 Kairui Song <ryncsn@gmail.com> wrote: > On Fri, Aug 8, 2025 at 3:48 PM Chris Li <chrisl@kernel.org> wrote: > > > > This the alloc_swap_scan_list() will scan the whole list or the first > > cluster. > > Hi Chris, > > This sentence reads strange to me, but English is not my native > language so I'm not very sure about it. Yes, I rewrote this to : alloc_swap_scan_list() will scan the whole list or the first cluster. : : This reduces the repeat patterns of isolating a cluster then scanning that : cluster. As a result, cluster_alloc_swap_entry() is shorter and : shallower. : : No functional change. Which is hopefully accurate. LLMs do an awesome job of doing this, although one should carefully review the output. Here's gemini.google.com: : alloc_swap_scan_list() now scans either the entire list or just the : first cluster. This change eliminates the repetitive pattern of : isolating and then scanning a cluster. As a result, the function : cluster_alloc_swap_entry() is now shorter and less complex. There are : no functional changes to the code's behavior.
On Mon, Aug 11, 2025 at 9:24 PM Andrew Morton <akpm@linux-foundation.org> wrote: > > On Sat, 9 Aug 2025 03:51:48 +0800 Kairui Song <ryncsn@gmail.com> wrote: > > > On Fri, Aug 8, 2025 at 3:48 PM Chris Li <chrisl@kernel.org> wrote: > > > > > > This the alloc_swap_scan_list() will scan the whole list or the first > > > cluster. > > > > Hi Chris, > > > > This sentence reads strange to me, but English is not my native > > language so I'm not very sure about it. Ack. My bad. > > Yes, I rewrote this to > > > : alloc_swap_scan_list() will scan the whole list or the first cluster. > : > : This reduces the repeat patterns of isolating a cluster then scanning that > : cluster. As a result, cluster_alloc_swap_entry() is shorter and > : shallower. > : > : No functional change. > > Which is hopefully accurate. > > > LLMs do an awesome job of doing this, although one should carefully > review the output. Here's gemini.google.com: > > : alloc_swap_scan_list() now scans either the entire list or just the > : first cluster. This change eliminates the repetitive pattern of > : isolating and then scanning a cluster. As a result, the function > : cluster_alloc_swap_entry() is now shorter and less complex. There are > : no functional changes to the code's behavior. > Thanks I will do a V3 and use something like that. I spot some other minor cleanup required. Might just add it to the clean up series. Chris
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