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t=1746708951; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=c1U4rZGx6XERUK703NiiO7qOrMXmSyQcFqlgMieceks=; b=bjRVISLBtHX5DfYSngZXkcLernXd84uYnUhhfzmlqWxXU9ogXS+VA1nVBWV9C1OFAPhqrl DQwRHux+nTpoGHBRb/gwfeWNh70+kMhrQWYrv79phGNmIEqQXGFC49a2bgJPAHmLhdkwxt ZFp+s7KYFMcqqnWUY3eI9hBea5SP0YjYFVmEo5lpFa4k3vI9fvdUMGMfwOoBrm+8Sqls4s Qcc8j5qQPJHtt1XCPgM7RJ3+7TRvmqeAX2koZA923N0GkgcrDXU5tBajcjK6B2FKUpknB2 fqW9+yH4BbWCpv7P1pegCvQqVTLRoXqbMzB7aHwj2DPWWBsYwRCLPJGemPmoVw== Date: Thu, 8 May 2025 14:55:43 +0200 From: "Pankaj Raghav (Samsung)" To: Ryan Roberts Cc: Andrew Morton , "Matthew Wilcox (Oracle)" , Alexander Viro , Christian Brauner , Jan Kara , David Hildenbrand , Dave Chinner , Catalin Marinas , Will Deacon , Kalesh Singh , Zi Yan , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH v4 1/5] mm/readahead: Honour new_order in page_cache_ra_order() Message-ID: References: <20250430145920.3748738-1-ryan.roberts@arm.com> <20250430145920.3748738-2-ryan.roberts@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250430145920.3748738-2-ryan.roberts@arm.com> X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 9F72818001F X-Stat-Signature: mydhxxj76akd8k4ktbcwwn4ubtj6kumc X-Rspam-User: X-HE-Tag: 1746708955-23517 X-HE-Meta: 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 VkWScs2J 07KfnoVro+3Z3s5HbZ6zWyqFxmuBlDS2oQ9VnGmoQsH1AkecpkvVIs76c7d578KNTIndIUr0OZ3VrQ0dKTwhN2w017uUCgstvRYLFhHwmm8iSpQiFZ/MK9B+NA5Jok/RIsNNzox3mTaV4S4g4jWXp3+FCtddYHCjOP1WrV9HyulhusNylPjtUognJxSjNqmq+39HcN4l2t3sC8euxhoggdAeKBLGKOQU5cArqnlhDLOOj8paalEh1ZMET2/A7ufVYbh/EM+vIZ44TkLbRQzm5vSgRTz5c09Q3Meekj8TO+v9bxBGEkFIudmllWJzJM8ZTFpKDyy6J3IflPv0A7gU0kop6eIoFQE8nQ/lktNREo/yAO0m/o9IWTLErGZYXabmFToAGoebUiCgT1t4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hey Ryan, On Wed, Apr 30, 2025 at 03:59:14PM +0100, Ryan Roberts wrote: > FOLIO 0x0001a000 0x0001b000 4096 26 27 1 0 > FOLIO 0x0001b000 0x0001c000 4096 27 28 1 0 > FOLIO 0x0001c000 0x0001d000 4096 28 29 1 0 > FOLIO 0x0001d000 0x0001e000 4096 29 30 1 0 > FOLIO 0x0001e000 0x0001f000 4096 30 31 1 0 > FOLIO 0x0001f000 0x00020000 4096 31 32 1 0 > FOLIO 0x00020000 0x00024000 16384 32 36 4 2 > FOLIO 0x00024000 0x00028000 16384 36 40 4 2 > FOLIO 0x00028000 0x0002c000 16384 40 44 4 2 > FOLIO 0x0002c000 0x00030000 16384 44 48 4 2 > ... > > Signed-off-by: Ryan Roberts > --- > mm/readahead.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/mm/readahead.c b/mm/readahead.c > index 6a4e96b69702..8bb316f5a842 100644 > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -479,9 +479,6 @@ void page_cache_ra_order(struct readahead_control *ractl, > So we always had a fallback to do_page_cache_ra() if the size of the readahead is less than 4 pages (16k). I think this was there because we were adding `2` to the new_order: unsigned int min_ra_size = max(4, mapping_min_folio_nrpages(mapping)); /* * Fallback when size < min_nrpages as each folio should be * at least min_nrpages anyway. */ if (!mapping_large_folio_support(mapping) || ra->size < min_ra_size) goto fallback; > limit = min(limit, index + ra->size - 1); > > - if (new_order < mapping_max_folio_order(mapping)) > - new_order += 2; Now that you have moved this, we could make the lhs of the max to be 2 (8k) instead of 4(16k). - unsigned int min_ra_size = max(4, mapping_min_folio_nrpages(mapping)); + unsigned int min_ra_size = max(2, mapping_min_folio_nrpages(mapping)); I think if we do that, we might ramp up to 8k sooner rather than jumping from 4k to 16k directly? > - > new_order = min(mapping_max_folio_order(mapping), new_order); > new_order = min_t(unsigned int, new_order, ilog2(ra->size)); > new_order = max(new_order, min_order); > @@ -683,6 +680,7 @@ void page_cache_async_ra(struct readahead_control *ractl, > ra->size = get_next_ra_size(ra, max_pages); > ra->async_size = ra->size; > readit: > + order += 2; > ractl->_index = ra->start; > page_cache_ra_order(ractl, ra, order); > } > -- > 2.43.0 > -- Pankaj