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From: Mel Gorman <mgorman@suse.de>
To: Rik van Riel <riel@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	torvalds@linux-foundation.org, peterz@infradead.org,
	mingo@kernel.org, aarcange@redhat.com
Subject: Re: [PATCH] sched,numa,mm: revert to checking pmd/pte_write instead of VMA flags
Date: Sun, 11 Sep 2016 17:24:02 +0100	[thread overview]
Message-ID: <20160911162402.GA2775@suse.de> (raw)
In-Reply-To: <20160908213053.07c992a9@annuminas.surriel.com>

On Thu, Sep 08, 2016 at 09:30:53PM -0400, Rik van Riel wrote:
> Commit 4d9424669946 ("mm: convert p[te|md]_mknonnuma and remaining
> page table manipulations") changed NUMA balancing from _PAGE_NUMA
> to using PROT_NONE, and was quickly found to introduce a regression
> with NUMA grouping.
> 
> It was followed up by these changesets:
> 
> 53da3bc2ba9e ("mm: fix up numa read-only thread grouping logic")
> bea66fbd11af ("mm: numa: group related processes based on VMA flags instead of page table flags")
> b191f9b106ea ("mm: numa: preserve PTE write permissions across a NUMA hinting fault")
> 
> The first of those two changesets try alternate approaches to NUMA
> grouping, which apparently do not work as well as looking at the PTE
> write permissions.
> 
> The latter patch preserves the PTE write permissions across a NUMA
> protection fault. However, it forgets to revert the condition for
> whether or not to group tasks together back to what it was before
> 3.19, even though the information is now preserved in the page tables
> once again.
> 
> This patch brings the NUMA grouping heuristic back to what it was
> before changeset 4d9424669946, which the changelogs of subsequent
> changesets suggest worked best.
> 
> We have all the information again. We should probably use it.
> 

Patch looks ok other than the comment above the second hunk being out of
date. Out of curiousity, what workload benefitted from this? I saw a mix
of marginal results when I ran this on a 2-socket and 4-socket box.

-- 
Mel Gorman
SUSE Labs

WARNING: multiple messages have this Message-ID (diff)
From: Mel Gorman <mgorman@suse.de>
To: Rik van Riel <riel@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	torvalds@linux-foundation.org, peterz@infradead.org,
	mingo@kernel.org, aarcange@redhat.com
Subject: Re: [PATCH] sched,numa,mm: revert to checking pmd/pte_write instead of VMA flags
Date: Sun, 11 Sep 2016 17:24:02 +0100	[thread overview]
Message-ID: <20160911162402.GA2775@suse.de> (raw)
In-Reply-To: <20160908213053.07c992a9@annuminas.surriel.com>

On Thu, Sep 08, 2016 at 09:30:53PM -0400, Rik van Riel wrote:
> Commit 4d9424669946 ("mm: convert p[te|md]_mknonnuma and remaining
> page table manipulations") changed NUMA balancing from _PAGE_NUMA
> to using PROT_NONE, and was quickly found to introduce a regression
> with NUMA grouping.
> 
> It was followed up by these changesets:
> 
> 53da3bc2ba9e ("mm: fix up numa read-only thread grouping logic")
> bea66fbd11af ("mm: numa: group related processes based on VMA flags instead of page table flags")
> b191f9b106ea ("mm: numa: preserve PTE write permissions across a NUMA hinting fault")
> 
> The first of those two changesets try alternate approaches to NUMA
> grouping, which apparently do not work as well as looking at the PTE
> write permissions.
> 
> The latter patch preserves the PTE write permissions across a NUMA
> protection fault. However, it forgets to revert the condition for
> whether or not to group tasks together back to what it was before
> 3.19, even though the information is now preserved in the page tables
> once again.
> 
> This patch brings the NUMA grouping heuristic back to what it was
> before changeset 4d9424669946, which the changelogs of subsequent
> changesets suggest worked best.
> 
> We have all the information again. We should probably use it.
> 

Patch looks ok other than the comment above the second hunk being out of
date. Out of curiousity, what workload benefitted from this? I saw a mix
of marginal results when I ran this on a 2-socket and 4-socket box.

-- 
Mel Gorman
SUSE Labs

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  reply	other threads:[~2016-09-11 16:24 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-09  1:30 [PATCH] sched,numa,mm: revert to checking pmd/pte_write instead of VMA flags Rik van Riel
2016-09-09  1:30 ` Rik van Riel
2016-09-11 16:24 ` Mel Gorman [this message]
2016-09-11 16:24   ` Mel Gorman
2016-09-12 15:09   ` Rik van Riel
2016-09-14  9:25     ` Mel Gorman
2016-09-14  9:25       ` Mel Gorman
2016-09-13 22:07 ` [tip:sched/core] sched/numa, mm: Revert " tip-bot for Rik van Riel

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