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Subject: Re: [RFC PATCH 0/5] kmalloc-reclaimable caches
References: <20180524110011.1940-1-vbabka@suse.cz>
 <20180524114350.GA10323@bombadil.infradead.org>
From: Randy Dunlap <rdunlap@infradead.org>
Message-ID: <0944e1ed-60fe-36ce-ea06-936b3f595d5f@infradead.org>
Date: Thu, 24 May 2018 09:18:44 -0700
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To: Matthew Wilcox <willy@infradead.org>, Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, Roman Gushchin <guro@fb.com>, Michal Hocko <mhocko@kernel.org>, Johannes Weiner <hannes@cmpxchg.org>, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>, David Rientjes <rientjes@google.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Mel Gorman <mgorman@techsingularity.net>, Vijayanand Jitta <vjitta@codeaurora.org>

On 05/24/2018 04:43 AM, Matthew Wilcox wrote:
> On Thu, May 24, 2018 at 01:00:06PM +0200, Vlastimil Babka wrote:
>> Now for the issues a.k.a. why RFC:
>>
>> - I haven't find any other obvious users for reclaimable kmalloc (yet)
> 
> Is that a problem?  This sounds like it's enough to solve Facebook's
> problem.
> 
>> - the name of caches kmalloc-reclaimable-X is rather long
> 
> Yes; Christoph and I were talking about restricting slab names to 16 bytes
> just to make /proc/slabinfo easier to read.  How about
> 
> kmalloc-rec-128k
> 1234567890123456
> 
> Just makes it ;-)
> 
> Of course, somebody needs to do the work to use k/M instead of 4194304.
> We also need to bikeshed about when to switch; should it be:
> 
> kmalloc-rec-512
> kmalloc-rec-1024
> kmalloc-rec-2048
> kmalloc-rec-4096
> kmalloc-rec-8192
> kmalloc-rec-16k
> 
> or should it be
> 
> kmalloc-rec-512
> kmalloc-rec-1k
> kmalloc-rec-2k
> kmalloc-rec-4k
> kmalloc-rec-8k
> kmalloc-rec-16k
> 
> I slightly favour the latter as it'll be easier to implement.  Something like

Yes, agree, start using the suffix early.

> 
> 	static const char suffixes[3] = ' kM';
> 	int idx = 0;
> 
> 	while (size > 1024) {
> 		size /= 1024;
> 		idx++;
> 	}
> 
> 	sprintf("%d%c", size, suffices[idx]);

	                      suffixes
> 
> --


-- 
~Randy