From: Johannes Weiner <hannes@cmpxchg.org> To: Andres Freund <andres@anarazel.de> Cc: Rik van Riel <riel@redhat.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vlastimil Babka <vbabka@suse.cz> Subject: Re: Unhelpful caching decisions, possibly related to active/inactive sizing Date: Tue, 16 Feb 2016 14:29:46 -0500 [thread overview] Message-ID: <20160216192946.GA32543@cmpxchg.org> (raw) In-Reply-To: <20160212193553.6pugckvamgtk4x5q@alap3.anarazel.de> On Fri, Feb 12, 2016 at 08:35:53PM +0100, Andres Freund wrote: > To make an actually usable patch out of this it seems we'd have to add a > 'partial' argument to grab_cache_page_write_begin(), so writes to parts > of a page still cause the pages to be marked active. Is it preferrable > to change all callers of grab_cache_page_write_begin and > add_to_page_cache_lru or make them into wrapper functions, and call the > real deal when it matters? Personally, I'd prefer explicit arguments over another layer of wrappers, especially in the add_to_page_cache family. But it's possible others will disagree and only voice their opinion once you went through the hassle and sent a patch. > I do think that that's a reasonable algorithmic change, but nonetheless > its obviously possible that such changes regress some workloads. What's > the policy around testing such things? How about a FGP_WRITE that only sets the page's referenced bit, but doesn't activate or refault-activate the page? That way, pages that are only ever written would never get activated, but a single read mixed in would activate the page straightaway; either in mark_page_accessed() or through refault-activation.
WARNING: multiple messages have this Message-ID (diff)
From: Johannes Weiner <hannes@cmpxchg.org> To: Andres Freund <andres@anarazel.de> Cc: Rik van Riel <riel@redhat.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Vlastimil Babka <vbabka@suse.cz> Subject: Re: Unhelpful caching decisions, possibly related to active/inactive sizing Date: Tue, 16 Feb 2016 14:29:46 -0500 [thread overview] Message-ID: <20160216192946.GA32543@cmpxchg.org> (raw) In-Reply-To: <20160212193553.6pugckvamgtk4x5q@alap3.anarazel.de> On Fri, Feb 12, 2016 at 08:35:53PM +0100, Andres Freund wrote: > To make an actually usable patch out of this it seems we'd have to add a > 'partial' argument to grab_cache_page_write_begin(), so writes to parts > of a page still cause the pages to be marked active. Is it preferrable > to change all callers of grab_cache_page_write_begin and > add_to_page_cache_lru or make them into wrapper functions, and call the > real deal when it matters? Personally, I'd prefer explicit arguments over another layer of wrappers, especially in the add_to_page_cache family. But it's possible others will disagree and only voice their opinion once you went through the hassle and sent a patch. > I do think that that's a reasonable algorithmic change, but nonetheless > its obviously possible that such changes regress some workloads. What's > the policy around testing such things? How about a FGP_WRITE that only sets the page's referenced bit, but doesn't activate or refault-activate the page? That way, pages that are only ever written would never get activated, but a single read mixed in would activate the page straightaway; either in mark_page_accessed() or through refault-activation. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2016-02-16 19:30 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-02-09 16:52 Unhelpful caching decisions, possibly related to active/inactive sizing Andres Freund 2016-02-09 16:52 ` Andres Freund 2016-02-09 22:42 ` Johannes Weiner 2016-02-09 22:42 ` Johannes Weiner 2016-02-11 20:34 ` Rik van Riel 2016-02-11 20:34 ` Rik van Riel 2016-02-12 12:46 ` Andres Freund 2016-02-12 12:46 ` Andres Freund 2016-02-12 19:35 ` Andres Freund 2016-02-12 19:35 ` Andres Freund 2016-02-16 19:29 ` Johannes Weiner [this message] 2016-02-16 19:29 ` Johannes Weiner 2016-02-17 21:17 ` Rik van Riel 2016-02-17 21:17 ` Rik van Riel 2016-02-19 22:19 ` Andres Freund 2016-02-19 22:19 ` Andres Freund 2016-02-12 12:56 ` Andres Freund 2016-02-12 12:56 ` Andres Freund 2016-02-12 20:24 ` Johannes Weiner 2016-02-12 20:24 ` Johannes Weiner 2016-02-19 22:07 ` Andres Freund 2016-02-19 22:07 ` Andres Freund
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