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Message-ID: <ZxB9XpvYoDrYgnah@xsang-OptiPlex-9020>
Date: Thu, 17 Oct 2024 10:58:38 +0800
From: Oliver Sang <oliver.sang@...el.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
CC: <oe-lkp@...ts.linux.dev>, <lkp@...el.com>, <linux-kernel@...r.kernel.org>,
Andrew Morton <akpm@...ux-foundation.org>, Mark Brown <broonie@...nel.org>,
"Liam R. Howlett" <Liam.Howlett@...cle.com>, Vlastimil Babka
<vbabka@...e.cz>, Bert Karwatzki <spasswolf@....de>, Jeff Xu
<jeffxu@...omium.org>, Jiri Olsa <olsajiri@...il.com>, Kees Cook
<kees@...nel.org>, Lorenzo Stoakes <lstoakes@...il.com>, Matthew Wilcox
<willy@...radead.org>, "Paul E. McKenney" <paulmck@...nel.org>, Paul Moore
<paul@...l-moore.com>, Sidhartha Kumar <sidhartha.kumar@...cle.com>, "Suren
Baghdasaryan" <surenb@...gle.com>, <linux-mm@...ck.org>,
<ying.huang@...el.com>, <feng.tang@...el.com>, <fengwei.yin@...el.com>,
<oliver.sang@...el.com>
Subject: Re: [linus:master] [mm] cacded5e42: aim9.brk_test.ops_per_sec
-5.0% regression
hi, Lorenzo,
On Tue, Oct 15, 2024 at 08:56:28PM +0100, Lorenzo Stoakes wrote:
> On Fri, Oct 11, 2024 at 08:26:37AM +0100, Lorenzo Stoakes wrote:
> [snip]
>
> > Thanks for testing this suffices to rule this one out... I will try to get a
> > functional and reliable performance environment locally so I can properly
> > address this and then we can try something else.
> >
> > Thanks!
> > Lorenzo
> >
>
> OK Oliver, could you try the below patch? I have got aim9.brk up and
> running locally and for me this seems to address the issue.
>
> This is against Andrew's tree [0] in the mm-unstable branch. It should
> hopefully apply cleanly to -next also.
I found the patch still be able to applied to cacded5e42 cleanly, so below data
still based on this applyment.
$ git log --oneline 9cecc5dc893886
9cecc5dc893886 mm: add expand-only VMA merge mode and optimise do_brk_flags()
cacded5e42b960 mm: avoid using vma_merge() for new VMAs
fc21959f74bc11 mm: abstract vma_expand() to use vma_merge_struct
...
again, if some patches in mm-unstable or -next have some impacts, please let me
know then I can re-apply the patch and do the tests again. thanks
by this patch, we do see performance recovery but not fully.
e.g. for
model: Granite Rapids
nr_node: 1
nr_cpu: 240
memory: 192G
we got better score from the patch than cacded5e42b960, but still 2.0%
regression than fc21959f74bc11 (the parent of cacded5e42b960)
=========================================================================================
compiler/cpufreq_governor/kconfig/rootfs/tbox_group/test/testcase/testtime:
gcc-12/performance/x86_64-rhel-8.3/debian-12-x86_64-20240206.cgz/lkp-gnr-1ap1/brk_test/aim9/300s
commit:
fc21959f74bc11 ("mm: abstract vma_expand() to use vma_merge_struct")
cacded5e42b960 ("mm: avoid using vma_merge() for new VMAs")
9cecc5dc893886 ("mm: add expand-only VMA merge mode and optimise do_brk_flags()")
fc21959f74bc1138 cacded5e42b9609b07b22d80c10 9cecc5dc89388676d1d0d47461c
---------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev
\ | \ | \
3220697 -6.0% 3028867 -2.0% 3156931 aim9.brk_test.ops_per_sec
similar results on other platforms, full data is attached as
fc21959f74bc11-cacded5e42b960-9cecc5dc893886
for
model: Emerald Rapids
nr_node: 4
nr_cpu: 256
memory: 256G
brand: INTEL(R) XEON(R) PLATINUM 8592+
=========================================================================================
compiler/cpufreq_governor/kconfig/rootfs/tbox_group/test/testcase/testtime:
gcc-12/performance/x86_64-rhel-8.3/debian-12-x86_64-20240206.cgz/lkp-emr-2sp1/brk_test/aim9/300s
commit:
fc21959f74bc11 ("mm: abstract vma_expand() to use vma_merge_struct")
cacded5e42b960 ("mm: avoid using vma_merge() for new VMAs")
9cecc5dc893886 ("mm: add expand-only VMA merge mode and optimise do_brk_flags()")
fc21959f74bc1138 cacded5e42b9609b07b22d80c10 9cecc5dc89388676d1d0d47461c
---------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev
\ | \ | \
3669298 -6.5% 3430070 -2.7% 3571699 aim9.brk_test.ops_per_sec
for
model: Sapphire Rapids
nr_node: 2
nr_cpu: 224
memory: 512G
brand: Intel(R) Xeon(R) Platinum 8480CTDX
=========================================================================================
compiler/cpufreq_governor/kconfig/rootfs/tbox_group/test/testcase/testtime:
gcc-12/performance/x86_64-rhel-8.3/debian-12-x86_64-20240206.cgz/lkp-spr-2sp4/brk_test/aim9/300s
commit:
fc21959f74bc11 ("mm: abstract vma_expand() to use vma_merge_struct")
cacded5e42b960 ("mm: avoid using vma_merge() for new VMAs")
9cecc5dc893886 ("mm: add expand-only VMA merge mode and optimise do_brk_flags()")
fc21959f74bc1138 cacded5e42b9609b07b22d80c10 9cecc5dc89388676d1d0d47461c
---------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev
\ | \ | \
3540976 -6.4% 3314159 -2.6% 3449384 aim9.brk_test.ops_per_sec
for
model: Ice Lake
nr_node: 2
nr_cpu: 64
memory: 256G
brand: Intel(R) Xeon(R) Gold 6346 CPU @ 3.10GHz
=========================================================================================
compiler/cpufreq_governor/kconfig/rootfs/tbox_group/test/testcase/testtime:
gcc-12/performance/x86_64-rhel-8.3/debian-12-x86_64-20240206.cgz/lkp-icl-2sp9/brk_test/aim9/300s
commit:
fc21959f74bc11 ("mm: abstract vma_expand() to use vma_merge_struct")
cacded5e42b960 ("mm: avoid using vma_merge() for new VMAs")
9cecc5dc893886 ("mm: add expand-only VMA merge mode and optimise do_brk_flags()")
fc21959f74bc1138 cacded5e42b9609b07b22d80c10 9cecc5dc89388676d1d0d47461c
---------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev
\ | \ | \
2667734 -5.6% 2518021 -1.0% 2640850 aim9.brk_test.ops_per_sec
for
test machine: 48 threads 2 sockets Intel(R) Xeon(R) CPU E5-2697 v2 @ 2.70GHz (Ivy Bridge-EP) with 64G memory
which we made the original report
=========================================================================================
compiler/cpufreq_governor/kconfig/rootfs/tbox_group/test/testcase/testtime:
gcc-12/performance/x86_64-rhel-8.3/debian-12-x86_64-20240206.cgz/lkp-ivb-2ep2/brk_test/aim9/300s
commit:
fc21959f74bc11 ("mm: abstract vma_expand() to use vma_merge_struct")
cacded5e42b960 ("mm: avoid using vma_merge() for new VMAs")
9cecc5dc893886 ("mm: add expand-only VMA merge mode and optimise do_brk_flags()")
fc21959f74bc1138 cacded5e42b9609b07b22d80c10 9cecc5dc89388676d1d0d47461c
---------------- --------------------------- ---------------------------
%stddev %change %stddev %change %stddev
\ | \ | \
1322908 -5.0% 1256536 -1.6% 1301387 aim9.brk_test.ops_per_sec
>
> Very much appreciated, thanks!
>
> [0]:https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/
>
> ----8<----
> From cee7f4196247de0da2b7632838fd36aee8b77e13 Mon Sep 17 00:00:00 2001
> From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
> Date: Tue, 15 Oct 2024 20:16:32 +0100
> Subject: [PATCH] mm: add expand-only VMA merge mode and optimise
> do_brk_flags()
>
> We know in advance that do_brk_flags() wants only to perform a VMA
> expansion (if the prior VMA is compatible), and that we assume no mergeable
> VMA follows it.
>
> These are the semantics of this function prior to the recent rewrite of the
> VMA merging logic, however we are now doing more work than necessary -
> positioning the VMA iterator at the prior VMA and performing tasks that are
> not required.
>
> Add a new field to the vmg struct to permit merge flags and add a new merge
> flag VMG_FLAG_JUST_EXPAND which implies this behaviour, and have
> do_brk_flags() use this.
>
> This fixes a reported performance regression in a brk() benchmarking suite.
> ---
> mm/mmap.c | 3 ++-
> mm/vma.c | 23 +++++++++++++++--------
> mm/vma.h | 16 ++++++++++++++++
> 3 files changed, 33 insertions(+), 9 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 02f7b45c3076..b99ba4cac9fe 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1741,7 +1741,8 @@ static int do_brk_flags(struct vma_iterator *vmi, struct vm_area_struct *vma,
> VMG_STATE(vmg, mm, vmi, addr, addr + len, flags, PHYS_PFN(addr));
>
> vmg.prev = vma;
> - vma_iter_next_range(vmi);
> + /* vmi is positioned at prev, which this mode expects. */
> + vmg.merge_flags = VMG_FLAG_JUST_EXPAND;
>
> if (vma_merge_new_range(&vmg))
> goto out;
> diff --git a/mm/vma.c b/mm/vma.c
> index 749c4881fd60..69ce9e07ab11 100644
> --- a/mm/vma.c
> +++ b/mm/vma.c
> @@ -562,6 +562,7 @@ struct vm_area_struct *vma_merge_new_range(struct vma_merge_struct *vmg)
> pgoff_t pgoff = vmg->pgoff;
> pgoff_t pglen = PHYS_PFN(end - start);
> bool can_merge_left, can_merge_right;
> + bool just_expand = vmg->merge_flags & VMG_FLAG_JUST_EXPAND;
>
> mmap_assert_write_locked(vmg->mm);
> VM_WARN_ON(vmg->vma);
> @@ -575,7 +576,7 @@ struct vm_area_struct *vma_merge_new_range(struct vma_merge_struct *vmg)
> return NULL;
>
> can_merge_left = can_vma_merge_left(vmg);
> - can_merge_right = can_vma_merge_right(vmg, can_merge_left);
> + can_merge_right = !just_expand && can_vma_merge_right(vmg, can_merge_left);
>
> /* If we can merge with the next VMA, adjust vmg accordingly. */
> if (can_merge_right) {
> @@ -590,7 +591,11 @@ struct vm_area_struct *vma_merge_new_range(struct vma_merge_struct *vmg)
> vmg->vma = prev;
> vmg->pgoff = prev->vm_pgoff;
>
> - vma_prev(vmg->vmi); /* Equivalent to going to the previous range */
> + /* In expand-only case we are already positioned here. */
> + if (!just_expand) {
> + /* Equivalent to going to the previous range. */
> + vma_prev(vmg->vmi);
> + }
> }
>
> /*
> @@ -604,12 +609,14 @@ struct vm_area_struct *vma_merge_new_range(struct vma_merge_struct *vmg)
> }
>
> /* If expansion failed, reset state. Allows us to retry merge later. */
> - vmg->vma = NULL;
> - vmg->start = start;
> - vmg->end = end;
> - vmg->pgoff = pgoff;
> - if (vmg->vma == prev)
> - vma_iter_set(vmg->vmi, start);
> + if (!just_expand) {
> + vmg->vma = NULL;
> + vmg->start = start;
> + vmg->end = end;
> + vmg->pgoff = pgoff;
> + if (vmg->vma == prev)
> + vma_iter_set(vmg->vmi, start);
> + }
>
> return NULL;
> }
> diff --git a/mm/vma.h b/mm/vma.h
> index 82354fe5edd0..8f8548958e41 100644
> --- a/mm/vma.h
> +++ b/mm/vma.h
> @@ -59,6 +59,19 @@ enum vma_merge_state {
> VMA_MERGE_SUCCESS,
> };
>
> +typedef unsigned long vma_merge_flags_t;
> +
> + /*
> + * If we can expand, simply do so. We know there is nothing to merge to the
> + * right.
> + *
> + * Does not reset state upon failure to merge.
> + *
> + * IMPORTANT: The VMA iterator is assumed to be positioned at the previous VMA,
> + * rather than at the gap.
> + */
> +#define VMG_FLAG_JUST_EXPAND (1 << 0)
> +
> /* Represents a VMA merge operation. */
> struct vma_merge_struct {
> struct mm_struct *mm;
> @@ -75,6 +88,7 @@ struct vma_merge_struct {
> struct mempolicy *policy;
> struct vm_userfaultfd_ctx uffd_ctx;
> struct anon_vma_name *anon_name;
> + vma_merge_flags_t merge_flags;
> enum vma_merge_state state;
> };
>
> @@ -99,6 +113,7 @@ static inline pgoff_t vma_pgoff_offset(struct vm_area_struct *vma,
> .flags = flags_, \
> .pgoff = pgoff_, \
> .state = VMA_MERGE_START, \
> + .merge_flags = 0, \
> }
>
> #define VMG_VMA_STATE(name, vmi_, prev_, vma_, start_, end_) \
> @@ -118,6 +133,7 @@ static inline pgoff_t vma_pgoff_offset(struct vm_area_struct *vma,
> .uffd_ctx = vma_->vm_userfaultfd_ctx, \
> .anon_name = anon_vma_name(vma_), \
> .state = VMA_MERGE_START, \
> + .merge_flags = 0, \
> }
>
> #ifdef CONFIG_DEBUG_VM_MAPLE_TREE
> --
> 2.46.2
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