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[95.203.26.253]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-54ea94ee6ccsm2001951e87.122.2025.05.06.02.42.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 06 May 2025 02:42:14 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Tue, 6 May 2025 11:42:12 +0200 To: Johannes Weiner , Vitaly Wool Cc: Vitaly Wool , linux-mm@kvack.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Nhat Pham , Shakeel Butt , Yosry Ahmed , Minchan Kim , Sergey Senozhatsky , Igor Belousov Subject: Re: [PATCH] mm/zblock: use vmalloc for page allocations Message-ID: References: <20250502080156.1672957-1-vitaly.wool@konsulko.se> <20250505142949.GB30814@cmpxchg.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250505142949.GB30814@cmpxchg.org> On Mon, May 05, 2025 at 10:29:49AM -0400, Johannes Weiner wrote: > On Fri, May 02, 2025 at 10:01:56AM +0200, Vitaly Wool wrote: > > static struct zblock_block *alloc_block(struct zblock_pool *pool, > > int block_type, gfp_t gfp, > > - unsigned long *handle) > > + unsigned long *handle, > > + unsigned int nid) > > { > > + struct block_list *block_list = &pool->block_lists[block_type]; > > + unsigned int num_pages = block_desc[block_type].num_pages; > > struct zblock_block *block; > > - struct block_list *block_list; > > + struct page *page = NULL; > > > > - block = (void *)__get_free_pages(gfp, block_desc[block_type].order); > > - if (!block) > > - return NULL; > > + if (!vmalloc_small_blocks && zblock_get_order(num_pages) >= 0) { > > + page = try_alloc_pages(nid, zblock_get_order(num_pages)); > > This is broken in several ways. > > The function is meant for NMI contexts - the "try" refers to > trylocking the freelists, in case whatever got interrupted was inside > the allocator already. This will fall back to vmalloc unpredictably. > > It also doesn't take a gfp parameter, which ignores the zswap ones, > and substitutes a set that doesn't make any sense in this context: > __GFP_NOMEMALLOC is counter productive inside reclaim; __GFP_ACCOUNT > wreaks complete havoc on how compressed memory is charged to cgroups > (double charging the wrong groups for shared blocks). > + "&& zblock_get_order(num_pages) >= 0" is always true? A fallback makes sense to use when order > 0, IMO. Or just stick fully to vmalloc. Another option is kvmalloc()/kvfree(). -- Uladzislau Rezki