| Message ID | 20250403053326.26860-1-shakeel.butt@linux.dev (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | memcg: vmalloc: simplify MEMCG_VMALLOC updates | expand |
On Wed 02-04-25 22:33:26, Shakeel Butt wrote: > The vmalloc region can either be charged to a single memcg or none. At > the moment kernel traverses all the pages backing the vmalloc region to > update the MEMCG_VMALLOC stat. However there is no need to look at all > the pages as all those pages will be charged to a single memcg or none. > Simplify the MEMCG_VMALLOC update by just looking at the first page of > the vmalloc region. I do not rememeber why this was done on page by page but I suspect originally we could have mixed more memcgs on one vm. The patch makes sense. > Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> Acked-by: Michal Hocko <mhocko@suse.com> Thanks! > --- > mm/vmalloc.c | 13 +++++-------- > 1 file changed, 5 insertions(+), 8 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 3ed720a787ec..cdae76994488 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -3370,12 +3370,12 @@ void vfree(const void *addr) > > if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS)) > vm_reset_perms(vm); > + if (vm->nr_pages && !(vm->flags & VM_MAP_PUT_PAGES)) > + mod_memcg_page_state(vm->pages[0], MEMCG_VMALLOC, -vm->nr_pages); > for (i = 0; i < vm->nr_pages; i++) { > struct page *page = vm->pages[i]; > > BUG_ON(!page); > - if (!(vm->flags & VM_MAP_PUT_PAGES)) > - mod_memcg_page_state(page, MEMCG_VMALLOC, -1); > /* > * High-order allocs for huge vmallocs are split, so > * can be freed as an array of order-0 allocations > @@ -3671,12 +3671,9 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask, > node, page_order, nr_small_pages, area->pages); > > atomic_long_add(area->nr_pages, &nr_vmalloc_pages); > - if (gfp_mask & __GFP_ACCOUNT) { > - int i; > - > - for (i = 0; i < area->nr_pages; i++) > - mod_memcg_page_state(area->pages[i], MEMCG_VMALLOC, 1); > - } > + if (gfp_mask & __GFP_ACCOUNT && area->nr_pages) > + mod_memcg_page_state(area->pages[0], MEMCG_VMALLOC, > + area->nr_pages); > > /* > * If not enough pages were obtained to accomplish an > -- > 2.47.1
On Wed, Apr 02, 2025 at 10:33:26PM -0700, Shakeel Butt wrote: > The vmalloc region can either be charged to a single memcg or none. At > the moment kernel traverses all the pages backing the vmalloc region to > update the MEMCG_VMALLOC stat. However there is no need to look at all > the pages as all those pages will be charged to a single memcg or none. > Simplify the MEMCG_VMALLOC update by just looking at the first page of > the vmalloc region. > > Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> > --- > mm/vmalloc.c | 13 +++++-------- > 1 file changed, 5 insertions(+), 8 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 3ed720a787ec..cdae76994488 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -3370,12 +3370,12 @@ void vfree(const void *addr) > > if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS)) > vm_reset_perms(vm); > + if (vm->nr_pages && !(vm->flags & VM_MAP_PUT_PAGES)) > + mod_memcg_page_state(vm->pages[0], MEMCG_VMALLOC, -vm->nr_pages); > Could you please add a comment stating that the first page should be modified? Yes, the comment is clear, but git blame/log takes time. Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com> -- Uladzislau Rezki
On Wed, Apr 02, 2025 at 10:33:26PM -0700, Shakeel Butt wrote: > The vmalloc region can either be charged to a single memcg or none. At > the moment kernel traverses all the pages backing the vmalloc region to > update the MEMCG_VMALLOC stat. However there is no need to look at all > the pages as all those pages will be charged to a single memcg or none. > Simplify the MEMCG_VMALLOC update by just looking at the first page of > the vmalloc region. > > Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> It's definitely pointless to handle each page with the stat being per-cgroup only. But I do wonder why it's not a regular vmstat item. There is no real reason it *should* be a private memcg stat, is there?
On Thu, Apr 03, 2025 at 01:17:22PM +0200, Uladzislau Rezki wrote: > On Wed, Apr 02, 2025 at 10:33:26PM -0700, Shakeel Butt wrote: > > The vmalloc region can either be charged to a single memcg or none. At > > the moment kernel traverses all the pages backing the vmalloc region to > > update the MEMCG_VMALLOC stat. However there is no need to look at all > > the pages as all those pages will be charged to a single memcg or none. > > Simplify the MEMCG_VMALLOC update by just looking at the first page of > > the vmalloc region. > > > > Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> > > --- > > mm/vmalloc.c | 13 +++++-------- > > 1 file changed, 5 insertions(+), 8 deletions(-) > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index 3ed720a787ec..cdae76994488 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -3370,12 +3370,12 @@ void vfree(const void *addr) > > > > if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS)) > > vm_reset_perms(vm); > > + if (vm->nr_pages && !(vm->flags & VM_MAP_PUT_PAGES)) > > + mod_memcg_page_state(vm->pages[0], MEMCG_VMALLOC, -vm->nr_pages); > > > Could you please add a comment stating that the first page should be > modified? > Sorry, what do you mean by first page should be modified? mod_memcg_page_state() will not modify the page but extract memcg from it and modify its vmalloc stat. > Yes, the comment is clear, but git blame/log takes time. > > Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Thanks. > > -- > Uladzislau Rezki
On Thu, Apr 03, 2025 at 12:47:41PM -0400, Johannes Weiner wrote: > On Wed, Apr 02, 2025 at 10:33:26PM -0700, Shakeel Butt wrote: > > The vmalloc region can either be charged to a single memcg or none. At > > the moment kernel traverses all the pages backing the vmalloc region to > > update the MEMCG_VMALLOC stat. However there is no need to look at all > > the pages as all those pages will be charged to a single memcg or none. > > Simplify the MEMCG_VMALLOC update by just looking at the first page of > > the vmalloc region. > > > > Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> > > It's definitely pointless to handle each page with the stat being > per-cgroup only. But I do wonder why it's not a regular vmstat item. > > There is no real reason it *should* be a private memcg stat, is there? Yes, it can be a regular vmstat item (enum node_stat_item). However then we have go over each page as node_stat_item are per-node and vmalloc region can have pages from different nodes (I think but let me check).
On Thu, Apr 03, 2025 at 11:20:18AM -0700, Shakeel Butt wrote: > On Thu, Apr 03, 2025 at 01:17:22PM +0200, Uladzislau Rezki wrote: > > On Wed, Apr 02, 2025 at 10:33:26PM -0700, Shakeel Butt wrote: > > > The vmalloc region can either be charged to a single memcg or none. At > > > the moment kernel traverses all the pages backing the vmalloc region to > > > update the MEMCG_VMALLOC stat. However there is no need to look at all > > > the pages as all those pages will be charged to a single memcg or none. > > > Simplify the MEMCG_VMALLOC update by just looking at the first page of > > > the vmalloc region. > > > > > > Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> > > > --- > > > mm/vmalloc.c | 13 +++++-------- > > > 1 file changed, 5 insertions(+), 8 deletions(-) > > > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > > index 3ed720a787ec..cdae76994488 100644 > > > --- a/mm/vmalloc.c > > > +++ b/mm/vmalloc.c > > > @@ -3370,12 +3370,12 @@ void vfree(const void *addr) > > > > > > if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS)) > > > vm_reset_perms(vm); > > > + if (vm->nr_pages && !(vm->flags & VM_MAP_PUT_PAGES)) > > > + mod_memcg_page_state(vm->pages[0], MEMCG_VMALLOC, -vm->nr_pages); > > > > > Could you please add a comment stating that the first page should be > > modified? > > > > Sorry, what do you mean by first page should be modified? > mod_memcg_page_state() will not modify the page but extract memcg from > it and modify its vmalloc stat. > I meant what you wrote in the commit message. A mod_memcg_page_state() can be invoked only on a first page within a mapped range, because the rest is anyway is associated with the same mem_cgroup struct. Just add a comment that we do not need to check all pages. Can you add it? -- Uladzislau Rezki
diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 3ed720a787ec..cdae76994488 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -3370,12 +3370,12 @@ void vfree(const void *addr) if (unlikely(vm->flags & VM_FLUSH_RESET_PERMS)) vm_reset_perms(vm); + if (vm->nr_pages && !(vm->flags & VM_MAP_PUT_PAGES)) + mod_memcg_page_state(vm->pages[0], MEMCG_VMALLOC, -vm->nr_pages); for (i = 0; i < vm->nr_pages; i++) { struct page *page = vm->pages[i]; BUG_ON(!page); - if (!(vm->flags & VM_MAP_PUT_PAGES)) - mod_memcg_page_state(page, MEMCG_VMALLOC, -1); /* * High-order allocs for huge vmallocs are split, so * can be freed as an array of order-0 allocations @@ -3671,12 +3671,9 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask, node, page_order, nr_small_pages, area->pages); atomic_long_add(area->nr_pages, &nr_vmalloc_pages); - if (gfp_mask & __GFP_ACCOUNT) { - int i; - - for (i = 0; i < area->nr_pages; i++) - mod_memcg_page_state(area->pages[i], MEMCG_VMALLOC, 1); - } + if (gfp_mask & __GFP_ACCOUNT && area->nr_pages) + mod_memcg_page_state(area->pages[0], MEMCG_VMALLOC, + area->nr_pages); /* * If not enough pages were obtained to accomplish an
The vmalloc region can either be charged to a single memcg or none. At the moment kernel traverses all the pages backing the vmalloc region to update the MEMCG_VMALLOC stat. However there is no need to look at all the pages as all those pages will be charged to a single memcg or none. Simplify the MEMCG_VMALLOC update by just looking at the first page of the vmalloc region. Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev> --- mm/vmalloc.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-)