From: Vlastimil Babka <vbabka@suse.cz>
To: "chenjun (AM)" <chenjun102@huawei.com>, Mike Rapoport <rppt@kernel.org>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"cl@linux.com" <cl@linux.com>,
"penberg@kernel.org" <penberg@kernel.org>,
"rientjes@google.com" <rientjes@google.com>,
"iamjoonsoo.kim@lge.com" <iamjoonsoo.kim@lge.com>,
"akpm@linux-foundation.org" <akpm@linux-foundation.org>,
Hyeonggon Yoo <42.hyeyoo@gmail.com>,
"xuqiang (M)" <xuqiang36@huawei.com>,
"Wangkefeng (OS Kernel Lab)" <wangkefeng.wang@huawei.com>,
Michal Hocko <mhocko@kernel.org>,
Mel Gorman <mgorman@techsingularity.net>
Subject: Re: [PATCH] mm/slub: Reduce memory consumption in extreme scenarios
Date: Wed, 29 Mar 2023 10:41:52 +0200 [thread overview]
Message-ID: <4f1096f0-cb6e-7cd2-5f41-c5e4b53fa407@suse.cz> (raw)
In-Reply-To: <c3a2280eff5c419ea14b6cad34474e08@huawei.com>
On 3/21/23 10:30, chenjun (AM) wrote:
> 在 2023/3/20 17:12, Mike Rapoport 写道:
>>>>
>>>> If we ignore __GFP_ZERO passed by kzalloc, kzalloc will not work.
>>>> Could we just unmask __GFP_RECLAIMABLE | __GFP_RECLAIM?
>>>>
>>>> pc.flags &= ~(__GFP_RECLAIMABLE | __GFP_RECLAIM)
>>>> pc.flags |= __GFP_THISNODE
>>>
>>> __GFP_RECLAIMABLE would be wrong, but also ignored as new_slab() does:
>>> flags & (GFP_RECLAIM_MASK | GFP_CONSTRAINT_MASK)
>>>
>>> which would filter out __GFP_ZERO as well. That's not a problem as kzalloc()
>>> will zero out the individual allocated objects, so it doesn't matter if we
>>> don't zero out the whole slab page.
>>>
>>> But I wonder, if we're not past due time for a helper e.g.
>>> gfp_opportunistic(flags) that would turn any allocation flags to a
>>> GFP_NOWAIT while keeping the rest of relevant flags intact, and thus there
>>> would be one canonical way to do it - I'm sure there's a number of places
>>> with their own variants now?
>>> With such helper we'd just add __GFP_THISNODE to the result here as that's
>>> specific to this particular opportunistic allocation.
>>
>> I like the idea, but maybe gfp_no_reclaim() would be clearer?
>>
>
> #define gfp_no_reclaim(gfpflag) (gfpflag & ~__GFP_DIRECT_RECLAIM)
I hoped for more feedback on the idea, but it's probably best proposed
outside of this slub-specific thread, so we could go for an open-coded
solution in slub for now.
Also just masking out __GFP_DIRECT_RECLAIM wouldn't be sufficient in any
case for the general solution/
> And here,
>
> pc.flags = gfp_no_reclaim(gfpflags) | __GFP_THISNODE.
I'd still suggest as earlier:
pc.flags = GFP_NOWAIT | __GFP_NOWARN |__GFP_THISNODE;
> Do I get it right?
next prev parent reply other threads:[~2023-03-29 8:41 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-14 12:34 [PATCH] mm/slub: Reduce memory consumption in extreme scenarios Chen Jun
2023-03-14 14:41 ` Vlastimil Babka
2023-03-17 11:32 ` chenjun (AM)
2023-03-17 12:06 ` Vlastimil Babka
2023-03-19 7:22 ` chenjun (AM)
2023-03-20 8:05 ` Vlastimil Babka
2023-03-20 9:12 ` Mike Rapoport
2023-03-21 9:30 ` chenjun (AM)
2023-03-29 8:41 ` Vlastimil Babka [this message]
2023-03-21 9:41 ` Vlastimil Babka
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