The patch titled
Subject: fork: optimize memcg_charge_kernel_stack() a bit
has been added to the -mm mm-nonmm-unstable branch. Its filename is
fork-optimize-memcg_charge_kernel_stack-a-bit.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fork-optimize-memcg_charge_kernel_stack-a-bit.patch
This patch will later appear in the mm-nonmm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Haifeng Xu <haifeng.xu@xxxxxxxxxx>
Subject: fork: optimize memcg_charge_kernel_stack() a bit
Date: Mon, 8 May 2023 06:44:58 +0000
Since commit f1c1a9ee00e4 ("fork: Move memcg_charge_kernel_stack()
into CONFIG_VMAP_STACK"), memcg_charge_kernel_stack() has been moved
into CONFIG_VMAP_STACK block, so the CONFIG_VMAP_STACK check can be
removed.
Furthermore, memcg_charge_kernel_stack() is only invoked by
alloc_thread_stack_node() instead of dup_task_struct(). If
memcg_kmem_charge_page() fails, the uncharge process is handled in
memcg_charge_kernel_stack() itself instead of free_thread_stack(),
so remove the incorrect comments.
If memcg_charge_kernel_stack() fails to charge pages used by kernel
stack, only charged pages need to be uncharged. It's unnecessary to
uncharge those pages which memory cgroup pointer is NULL.
Link: https://lkml.kernel.org/r/20230508064458.32855-1-haifeng.xu@xxxxxxxxxx
Signed-off-by: Haifeng Xu <haifeng.xu@xxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/fork.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)
--- a/kernel/fork.c~fork-optimize-memcg_charge_kernel_stack-a-bit
+++ a/kernel/fork.c
@@ -252,23 +252,20 @@ static int memcg_charge_kernel_stack(str
{
int i;
int ret;
+ int nr_charged = 0;
- BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
+ BUILD_BUG_ON(PAGE_SIZE % 1024 != 0);
BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 0);
if (ret)
goto err;
+ nr_charged++;
}
return 0;
err:
- /*
- * If memcg_kmem_charge_page() fails, page's memory cgroup pointer is
- * NULL, and memcg_kmem_uncharge_page() in free_thread_stack() will
- * ignore this page.
- */
- for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
+ for (i = 0; i < nr_charged; i++)
memcg_kmem_uncharge_page(vm->pages[i], 0);
return ret;
}
_
Patches currently in -mm which might be from haifeng.xu@xxxxxxxxxx are
memcg-oom-remove-unnecessary-check-in-mem_cgroup_oom_synchronize.patch
memcg-oom-remove-explicit-wakeup-in-mem_cgroup_oom_synchronize.patch
mm-oom-do-not-check-0-mask-in-out_of_memory.patch
fork-optimize-memcg_charge_kernel_stack-a-bit.patch
