[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <ZgQowqqGf-E7Cpcz@casper.infradead.org>
Date: Wed, 27 Mar 2024 14:10:10 +0000
From: Matthew Wilcox <willy@...radead.org>
To: Sasha Levin <sashal@...nel.org>
Cc: stable@...r.kernel.org, Rik van Riel <riel@...riel.com>,
Mel Gorman <mgorman@...hsingularity.net>,
Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
linux-kernel@...r.kernel.org
Subject: Re: FAILED: Patch "bounds: support non-power-of-two CONFIG_NR_CPUS"
failed to apply to 5.4-stable tree
On Wed, Mar 27, 2024 at 08:21:25AM -0400, Sasha Levin wrote:
> The patch below does not apply to the 5.4-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@...r.kernel.org>.
Looks like you just need a little more fuzz on the patch.
diff --git a/kernel/bounds.c b/kernel/bounds.c
index 9795d75b09b2..a94e3769347e 100644
--- a/kernel/bounds.c
+++ b/kernel/bounds.c
@@ -19,7 +19,7 @@ int main(void)
DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS);
DEFINE(MAX_NR_ZONES, __MAX_NR_ZONES);
#ifdef CONFIG_SMP
- DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS));
+ DEFINE(NR_CPUS_BITS, bits_per(CONFIG_NR_CPUS));
#endif
DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t));
/* End of constants */
> Thanks,
> Sasha
>
> ------------------ original commit in Linus's tree ------------------
>
> >From f2d5dcb48f7ba9e3ff249d58fc1fa963d374e66a Mon Sep 17 00:00:00 2001
> From: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> Date: Tue, 10 Oct 2023 15:55:49 +0100
> Subject: [PATCH] bounds: support non-power-of-two CONFIG_NR_CPUS
>
> ilog2() rounds down, so for example when PowerPC 85xx sets CONFIG_NR_CPUS
> to 24, we will only allocate 4 bits to store the number of CPUs instead of
> 5. Use bits_per() instead, which rounds up. Found by code inspection.
> The effect of this would probably be a misaccounting when doing NUMA
> balancing, so to a user, it would only be a performance penalty. The
> effects may be more wide-spread; it's hard to tell.
>
> Link: https://lkml.kernel.org/r/20231010145549.1244748-1-willy@infradead.org
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> Fixes: 90572890d202 ("mm: numa: Change page last {nid,pid} into {cpu,pid}")
> Reviewed-by: Rik van Riel <riel@...riel.com>
> Acked-by: Mel Gorman <mgorman@...hsingularity.net>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> ---
> kernel/bounds.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/bounds.c b/kernel/bounds.c
> index b529182e8b04f..c5a9fcd2d6228 100644
> --- a/kernel/bounds.c
> +++ b/kernel/bounds.c
> @@ -19,7 +19,7 @@ int main(void)
> DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS);
> DEFINE(MAX_NR_ZONES, __MAX_NR_ZONES);
> #ifdef CONFIG_SMP
> - DEFINE(NR_CPUS_BITS, ilog2(CONFIG_NR_CPUS));
> + DEFINE(NR_CPUS_BITS, bits_per(CONFIG_NR_CPUS));
> #endif
> DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t));
> #ifdef CONFIG_LRU_GEN
> --
> 2.43.0
>
>
>
>
Powered by blists - more mailing lists