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imf06.hostedemail.com; dkim=none; spf=pass (imf06.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1720103044; a=rsa-sha256; cv=none; b=LdGrvCnZNk4vR3xOfq6HZk2qrNiJkNvQ3EfZffRhI82w3wAg6kT28v5hJNI9Uf/0ZlbwQg Z0O/HYhpaE1kfbxWcXbGYXUwcsp8KGFVtakI6c8y0yf6DZUX+STbq6+k8v6J+W1JE1TlZv Viy6mEoYk8DHSj1a4R9489YpI76KB2I= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 35EA8367; Thu, 4 Jul 2024 07:24:40 -0700 (PDT) Received: from [10.1.29.168] (XHFQ2J9959.cambridge.arm.com [10.1.29.168]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 29AE33F766; Thu, 4 Jul 2024 07:24:12 -0700 (PDT) Message-ID: <98790338-0f86-4658-8dec-95e94b6d5c18@arm.com> Date: Thu, 4 Jul 2024 15:24:10 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 03/10] readahead: allocate folios with mapping_min_order in readahead Content-Language: en-GB To: "Pankaj Raghav (Samsung)" , david@fromorbit.com, willy@infradead.org, chandan.babu@oracle.com, djwong@kernel.org, brauner@kernel.org, akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, yang@os.amperecomputing.com, linux-mm@kvack.org, john.g.garry@oracle.com, linux-fsdevel@vger.kernel.org, hare@suse.de, p.raghav@samsung.com, mcgrof@kernel.org, gost.dev@samsung.com, cl@os.amperecomputing.com, linux-xfs@vger.kernel.org, hch@lst.de, Zi Yan References: <20240625114420.719014-1-kernel@pankajraghav.com> <20240625114420.719014-4-kernel@pankajraghav.com> From: Ryan Roberts In-Reply-To: <20240625114420.719014-4-kernel@pankajraghav.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 095E0180008 X-Stat-Signature: 7184tfkeqfxwwicpfz37bo3owpnc9rdw X-HE-Tag: 1720103055-357005 X-HE-Meta: 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 t91E1Qt3 iffHvzt0FwkkC90VDUabFfup1RjoUjfhyWkzspwIX4Cg8sG3iTGEJ4M0Di28CtyG5cni9be9VfzOPwBG01JJ0njuAlJNJRPQr7CLjr0hFDWap09+iOSw6gr98HE+CjueDv/PTwRdHqbz6k/3onM+tOmmDwbwCT8ELZR3GQg1eKQwW4HwMimu3QAK6oGTicz4i2nQRjFewcsCRyMOwixEHRWxq0Q== 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: On 25/06/2024 12:44, Pankaj Raghav (Samsung) wrote: > From: Pankaj Raghav > > page_cache_ra_unbounded() was allocating single pages (0 order folios) > if there was no folio found in an index. Allocate mapping_min_order folios > as we need to guarantee the minimum order if it is set. > While we are at it, rework the loop in page_cache_ra_unbounded() to > advance with the number of pages in a folio instead of just one page at > a time. > > page_cache_ra_order() tries to allocate folio to the page cache with a > higher order if the index aligns with that order. Modify it so that the > order does not go below the mapping_min_order requirement of the page > cache. This function will do the right thing even if the new_order passed > is less than the mapping_min_order. > When adding new folios to the page cache we must also ensure the index > used is aligned to the mapping_min_order as the page cache requires the > index to be aligned to the order of the folio. > > readahead_expand() is called from readahead aops to extend the range of > the readahead so this function can assume ractl->_index to be aligned with > min_order. > > Signed-off-by: Pankaj Raghav > Co-developed-by: Hannes Reinecke > Signed-off-by: Hannes Reinecke > --- > mm/readahead.c | 81 +++++++++++++++++++++++++++++++++++++++----------- > 1 file changed, 63 insertions(+), 18 deletions(-) > > diff --git a/mm/readahead.c b/mm/readahead.c > index 66058ae02f2e..2acfd6447d7b 100644 > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -206,9 +206,10 @@ void page_cache_ra_unbounded(struct readahead_control *ractl, > unsigned long nr_to_read, unsigned long lookahead_size) > { > struct address_space *mapping = ractl->mapping; > - unsigned long index = readahead_index(ractl); > + unsigned long ra_folio_index, index = readahead_index(ractl); > gfp_t gfp_mask = readahead_gfp_mask(mapping); > - unsigned long i; > + unsigned long mark, i = 0; > + unsigned int min_nrpages = mapping_min_folio_nrpages(mapping); > > /* > * Partway through the readahead operation, we will have added > @@ -223,10 +224,26 @@ void page_cache_ra_unbounded(struct readahead_control *ractl, > unsigned int nofs = memalloc_nofs_save(); > > filemap_invalidate_lock_shared(mapping); > + index = mapping_align_index(mapping, index); > + > + /* > + * As iterator `i` is aligned to min_nrpages, round_up the > + * difference between nr_to_read and lookahead_size to mark the > + * index that only has lookahead or "async_region" to set the > + * readahead flag. > + */ > + ra_folio_index = round_up(readahead_index(ractl) + nr_to_read - lookahead_size, > + min_nrpages); > + mark = ra_folio_index - index; > + if (index != readahead_index(ractl)) { > + nr_to_read += readahead_index(ractl) - index; > + ractl->_index = index; > + } > + > /* > * Preallocate as many pages as we will need. > */ > - for (i = 0; i < nr_to_read; i++) { > + while (i < nr_to_read) { > struct folio *folio = xa_load(&mapping->i_pages, index + i); > int ret; > > @@ -240,12 +257,13 @@ void page_cache_ra_unbounded(struct readahead_control *ractl, > * not worth getting one just for that. > */ For the case that the folio is already in the xarray, perhaps its worth asserting that the folio is at least min_nrpages? > read_pages(ractl); > - ractl->_index++; > - i = ractl->_index + ractl->_nr_pages - index - 1; > + ractl->_index += min_nrpages; > + i = ractl->_index + ractl->_nr_pages - index; > continue; > } > > - folio = filemap_alloc_folio(gfp_mask, 0); > + folio = filemap_alloc_folio(gfp_mask, > + mapping_min_folio_order(mapping)); > if (!folio) > break; > > @@ -255,14 +273,15 @@ void page_cache_ra_unbounded(struct readahead_control *ractl, > if (ret == -ENOMEM) > break; > read_pages(ractl); > - ractl->_index++; > - i = ractl->_index + ractl->_nr_pages - index - 1; > + ractl->_index += min_nrpages; > + i = ractl->_index + ractl->_nr_pages - index; > continue; > } > - if (i == nr_to_read - lookahead_size) > + if (i == mark) > folio_set_readahead(folio); > ractl->_workingset |= folio_test_workingset(folio); > - ractl->_nr_pages++; > + ractl->_nr_pages += min_nrpages; > + i += min_nrpages; > } > > /* > @@ -492,13 +511,19 @@ void page_cache_ra_order(struct readahead_control *ractl, > { > struct address_space *mapping = ractl->mapping; > pgoff_t index = readahead_index(ractl); > + unsigned int min_order = mapping_min_folio_order(mapping); > pgoff_t limit = (i_size_read(mapping->host) - 1) >> PAGE_SHIFT; > pgoff_t mark = index + ra->size - ra->async_size; > unsigned int nofs; > int err = 0; > gfp_t gfp = readahead_gfp_mask(mapping); > + unsigned int min_ra_size = max(4, mapping_min_folio_nrpages(mapping)); > > - if (!mapping_large_folio_support(mapping) || ra->size < 4) > + /* > + * 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); > @@ -507,11 +532,20 @@ void page_cache_ra_order(struct readahead_control *ractl, > new_order += 2; > 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); > } > > /* See comment in page_cache_ra_unbounded() */ > nofs = memalloc_nofs_save(); > filemap_invalidate_lock_shared(mapping); > + /* > + * If the new_order is greater than min_order and index is > + * already aligned to new_order, then this will be noop as index > + * aligned to new_order should also be aligned to min_order. > + */ > + ractl->_index = mapping_align_index(mapping, index); > + index = readahead_index(ractl); > + > while (index <= limit) { > unsigned int order = new_order; > > @@ -519,7 +553,7 @@ void page_cache_ra_order(struct readahead_control *ractl, > if (index & ((1UL << order) - 1)) > order = __ffs(index); > /* Don't allocate pages past EOF */ > - while (index + (1UL << order) - 1 > limit) > + while (order > min_order && index + (1UL << order) - 1 > limit) > order--; > err = ra_alloc_folio(ractl, index, mark, order, gfp); > if (err) > @@ -783,8 +817,15 @@ void readahead_expand(struct readahead_control *ractl, > struct file_ra_state *ra = ractl->ra; > pgoff_t new_index, new_nr_pages; > gfp_t gfp_mask = readahead_gfp_mask(mapping); > + unsigned long min_nrpages = mapping_min_folio_nrpages(mapping); > + unsigned int min_order = mapping_min_folio_order(mapping); > > new_index = new_start / PAGE_SIZE; > + /* > + * Readahead code should have aligned the ractl->_index to > + * min_nrpages before calling readahead aops. > + */ > + VM_BUG_ON(!IS_ALIGNED(ractl->_index, min_nrpages)); > > /* Expand the leading edge downwards */ > while (ractl->_index > new_index) { > @@ -794,9 +835,11 @@ void readahead_expand(struct readahead_control *ractl, > if (folio && !xa_is_value(folio)) > return; /* Folio apparently present */ > > - folio = filemap_alloc_folio(gfp_mask, 0); > + folio = filemap_alloc_folio(gfp_mask, min_order); > if (!folio) > return; > + > + index = mapping_align_index(mapping, index); > if (filemap_add_folio(mapping, folio, index, gfp_mask) < 0) { > folio_put(folio); > return; > @@ -806,7 +849,7 @@ void readahead_expand(struct readahead_control *ractl, > ractl->_workingset = true; > psi_memstall_enter(&ractl->_pflags); > } > - ractl->_nr_pages++; > + ractl->_nr_pages += min_nrpages; > ractl->_index = folio->index; > } > > @@ -821,9 +864,11 @@ void readahead_expand(struct readahead_control *ractl, > if (folio && !xa_is_value(folio)) > return; /* Folio apparently present */ > > - folio = filemap_alloc_folio(gfp_mask, 0); > + folio = filemap_alloc_folio(gfp_mask, min_order); > if (!folio) > return; > + > + index = mapping_align_index(mapping, index); > if (filemap_add_folio(mapping, folio, index, gfp_mask) < 0) { > folio_put(folio); > return; > @@ -833,10 +878,10 @@ void readahead_expand(struct readahead_control *ractl, > ractl->_workingset = true; > psi_memstall_enter(&ractl->_pflags); > } > - ractl->_nr_pages++; > + ractl->_nr_pages += min_nrpages; > if (ra) { > - ra->size++; > - ra->async_size++; > + ra->size += min_nrpages; > + ra->async_size += min_nrpages; > } > } > }