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From:   Tianxianting <tian.xianting@h3c.com>
To:     Michal Hocko <mhocko@suse.com>
CC:     "akpm@linux-foundation.org" <akpm@linux-foundation.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] mm: vmscan: avoid a unnecessary reschedule in
 shrink_slab()
Thread-Topic: [PATCH] mm: vmscan: avoid a unnecessary reschedule in
 shrink_slab()
Thread-Index: AQHWo29cMaRbAMdQE0ycFn5GylDeeqmZnPOAgACJFdD//4YYAIAAiVZw//+CoICAAJNtUA==
Date:   Fri, 16 Oct 2020 14:33:13 +0000
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Thanks for the explain.
I got it.

-----Original Message-----
From: Michal Hocko [mailto:mhocko@suse.com] 
Sent: Friday, October 16, 2020 9:45 PM
To: tianxianting (RD) <tian.xianting@h3c.com>
Cc: akpm@linux-foundation.org; linux-mm@kvack.org; linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm: vmscan: avoid a unnecessary reschedule in shrink_slab()

On Fri 16-10-20 13:20:41, Tianxianting wrote:
> Thanks
> I understood what you said :)
> But whether it is proper to check reschedule in every loop when lock is taken? 

I do not see any actual problem TBH. cond_resched is mostly to increase interactivity for non preemptible kernel. It can reduce throughput but this is a memory reclaim path and I do not expect this to contribute to any moderate hot paths. Direct reclaim doesn't really count as a hot path.

--
Michal Hocko
SUSE Labs