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smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=AUUu8yrt; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="AUUu8yrt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CF9681F000E9; Thu, 28 May 2026 14:29:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779978570; bh=5BA6dKKBNlOGQi64KHMmEqDOAVzKaNmuRrG2iObP2CM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=AUUu8yrtNtz9lxvBi5v8RskjXS8SYRIECkH8bIL4SrxFeTsTXmvL8y6433fDYU4HM ClQhyqWH5WyBBJOJRIXbQJbJC3B4OjZ/GIkL9SPsqXu7NG3Wi7ZOPlbPULz+oIWcAB /XzKXAxW/wfgevx2iJ9u/b5O3NC2ciKPK8T61u3B2UoeuMZloBg8bSEyUXVQgV7utN rxopDswt8KeAnKtUCrNB1NdkaWtXi8iHId31SvIwTpeKOKFBwSSABZHenwFeXeAjQ8 gDgweFe0fAaWVBaG2FiBxhIgOy0NB+1Ipi0FrGx+90iQckdBPxMxpXzgOogaAgTbj1 DHpxqskbLJd6w== Message-ID: Date: Thu, 28 May 2026 16:29:26 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/page_alloc: fix deferred compaction accounting Content-Language: en-US To: fujunjie , Andrew Morton Cc: Brendan Jackman , Johannes Weiner , Michal Hocko , Suren Baghdasaryan , Zi Yan , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Charan Teja Kalla , David Rientjes References: From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/26/26 11:12, fujunjie wrote: > COMPACT_DEFERRED means compaction did not start because past failures > caused the zone to be deferred. try_to_compact_pages() returns the > maximum result seen while walking the zonelist, so a final > COMPACT_DEFERRED result means no later zone reported that compaction > actually ran. > > __alloc_pages_direct_compact() skips COMPACTSTALL and COMPACTFAIL > accounting when try_to_compact_pages() returns COMPACT_SKIPPED, but not > when it returns COMPACT_DEFERRED. A deferred-only direct compaction > attempt can therefore look like a stall, and then a failure if the > allocation still cannot be satisfied. > > Treat COMPACT_DEFERRED like COMPACT_SKIPPED in this accounting path. If > a later zone runs compaction and returns a result above COMPACT_DEFERRED, > or compact_zone_order() reports COMPACT_SUCCESS for a captured page, the > final result is not COMPACT_DEFERRED and the existing accounting still > runs. > > Signed-off-by: fujunjie Hm I wonder why didn't we do that right away in 06dac2f467fe ("mm: compaction: update the COMPACT[STALL|FAIL] events properly"), seems like even back then there was nothing that would e.g. convert _DEFERED to _SKIPPED from try_to_compact_pages(), and the changelog did mention deferred. So I guess for posterity we could do (but no Cc: stable, it's just stats). Fixes: 06dac2f467fe ("mm: compaction: update the COMPACT[STALL|FAIL] events properly") Reviewed-by: Vlastimil Babka (SUSE) Thanks! > --- > mm/page_alloc.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 23c7298d3be2..ddeb79fa12db 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -4161,7 +4161,8 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, > psi_memstall_leave(&pflags); > delayacct_compact_end(); > > - if (*compact_result == COMPACT_SKIPPED) > + if (*compact_result == COMPACT_SKIPPED || > + *compact_result == COMPACT_DEFERRED) > return NULL; > /* > * At least in one zone compaction wasn't deferred or skipped, so let's > > base-commit: e8c2f9fdadee7cbc75134dc463c1e0d856d6e5c7