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Thu, 26 Mar 2026 16:21:42 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id eyLhGRZdxWlFIQAAD6G6ig (envelope-from ); Thu, 26 Mar 2026 16:21:42 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 1091BA0976; Thu, 26 Mar 2026 17:21:34 +0100 (CET) Date: Thu, 26 Mar 2026 17:21:34 +0100 From: Jan Kara To: Usama Arif Cc: Jan Kara , david@kernel.org, ryan.roberts@arm.com, Andrew Morton , willy@infradead.org, linux-mm@kvack.org, r@hev.cc, ajd@linux.ibm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, brauner@kernel.org, catalin.marinas@arm.com, dev.jain@arm.com, kees@kernel.org, kevin.brodsky@arm.com, lance.yang@linux.dev, Liam.Howlett@oracle.com, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, lorenzo.stoakes@oracle.com, mhocko@suse.com, npache@redhat.com, pasha.tatashin@soleen.com, rmclure@linux.ibm.com, rppt@kernel.org, surenb@google.com, vbabka@kernel.org, Al Viro , wilts.infradead.org@quack3.kvack.org, ziy@nvidia.com, hannes@cmpxchg.org, kas@kernel.org, shakeel.butt@linux.dev, kernel-team@meta.com Subject: Re: [PATCH v2 2/4] mm: replace exec_folio_order() with generic preferred_exec_order() Message-ID: <4pzoddjdplps6wzf7hluwjg7jty7tmrwkq5jk7qzer4kur5o4q@7ge6uatpmkex> References: <20260320140315.979307-1-usama.arif@linux.dev> <20260320140315.979307-3-usama.arif@linux.dev> <0ce07bc5-6365-4c54-90e2-4e56ad2b7465@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0ce07bc5-6365-4c54-90e2-4e56ad2b7465@linux.dev> X-Rspamd-Action: no action X-Rspam-User: X-Stat-Signature: 37b8pj546paqjzh6hnw454uyfym71uub X-Rspamd-Queue-Id: 02A3F40015 X-Rspamd-Server: rspam09 X-HE-Tag: 1774542104-144140 X-HE-Meta: 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 6+LZZrVP cHwl7p/gSrCfoTLZcvyDAux9ziGFXOkFSMXo0oKgfBNx8LISOj0Z2zz4S2HsjqiYpC0QXDG6UxWa/Psy6ajDYjp0A8199ZaVMMRWLX3XqJjmC94TyT46dKUa0jClbpM6BkGa7QMerNb0KIbspOh6ZjzjY8n4mlF8nekbO6Wt3biL9LlNDieXZpdpWIjmEylcXT+lhd9jp+Sj32bW/g4lG8zQbEKVwYvwCiLp1p4rHp6JmER3iXMceghPkXQ0s9ZzNr1aUUPFq/RweCkY7FNuAhfT2LeAvw37I1IGpa9+e/Ccj7QW7GwKOHFsqrj3aCNaPchdkSD3ub6buoGo7s+/kLjNWk8yhywiTKNWZSFAKybpoCKH2xgpwvvSnoLqzUfEuZBJg9cGASdyjdBU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu 26-03-26 08:40:21, Usama Arif wrote: > On 20/03/2026 17:42, Jan Kara wrote: > >> + /* Step down under memory pressure */ > >> + gfp = mapping_gfp_mask(vma->vm_file->f_mapping); > >> + zone = first_zones_zonelist(node_zonelist(numa_node_id(), gfp), > >> + gfp_zone(gfp), NULL)->zone; > >> + if (zone) { > >> + while (order > 0 && > >> + !zone_watermark_ok(zone, order, > >> + high_wmark_pages(zone), 0, 0)) > >> + order--; > >> + } > > > > It looks wrong for this logic to be here. Trimming order based on memory > > pressure makes sense (and we've already got reports that on memory limited > > devices large order folios in the page cache have too big memory overhead > > so we'll likely need to handle that for page cache allocations in general) > > but IMHO it belongs to page_cache_ra_order() or some other common place > > like that. > > > > Honza > > So I have been thinking about this. readahead_gfp_mask() already sets > __GFP_NORETRY, so we wont try aggressive reclaim/compaction to satisfy > the allocation. page_cache_ra_order() falls through to the fallback path > faulting in order 0 page when allocation is not satsified. > > So the allocator already naturally steps down under memory pressure, > the explicit zone_watermark_ok() loop might be redundant? Probably yes. I still think we'll have to somehow better tweak the used order based on expected size of the page cache (2M folios seem unreasonably large for a machine that has e.g. 1G of memory in total, even if it has enough free memory at this point in time - we'll benefit from smaller folios and thus finer grained folio activity tracking for such cases). But that's not for this patch set. > What are your thoughts on just setting > ra->order = min(HPAGE_PMD_ORDER, ilog2(SZ_2M >> PAGE_SHIFT))? > We can do the higher orlder allocation with gfp &= ~__GFP_RECLAIM > for the VM_EXEC case. Yes, it's simple and it makes sense to me so if others are fine with it... Honza -- Jan Kara SUSE Labs, CR