From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f169.google.com (mail-ig0-f169.google.com [209.85.213.169]) by kanga.kvack.org (Postfix) with ESMTP id 382316B0255 for ; Tue, 22 Sep 2015 13:09:50 -0400 (EDT) Received: by igcpb10 with SMTP id pb10so103657465igc.1 for ; Tue, 22 Sep 2015 10:09:50 -0700 (PDT) Received: from mail-ig0-x22a.google.com (mail-ig0-x22a.google.com. [2607:f8b0:4001:c05::22a]) by mx.google.com with ESMTPS id y3si13665018igl.47.2015.09.22.10.09.49 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 22 Sep 2015 10:09:49 -0700 (PDT) Received: by igxx6 with SMTP id x6so13483330igx.1 for ; Tue, 22 Sep 2015 10:09:49 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <20150916134857.e4a71f601a1f68cfa16cb361@gmail.com> <20150916135048.fbd50fac5e91244ab9731b82@gmail.com> From: Dan Streetman Date: Tue, 22 Sep 2015 13:09:09 -0400 Message-ID: Subject: Re: [PATCH 1/2] zbud: allow PAGE_SIZE allocations Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Vitaly Wool Cc: Andrew Morton , Minchan Kim , Sergey Senozhatsky , linux-kernel , Linux-MM , Seth Jennings On Tue, Sep 22, 2015 at 6:18 AM, Vitaly Wool wrote: > Hi Dan, > > On Mon, Sep 21, 2015 at 6:17 PM, Dan Streetman wrote: >> Please make sure to cc Seth also, he's the owner of zbud. > > Sure :) > > >>> @@ -514,8 +552,17 @@ int zbud_reclaim_page(struct zbud_pool *pool, unsigned int retries) >>> return -EINVAL; >>> } >>> for (i = 0; i < retries; i++) { >>> - zhdr = list_tail_entry(&pool->lru, struct zbud_header, lru); >>> - list_del(&zhdr->lru); >>> + page = list_tail_entry(&pool->lru, struct page, lru); >>> + zhdr = page_address(page); >>> + list_del(&page->lru); >>> + /* Uncompressed zbud page? just run eviction and free it */ >>> + if (page->flags & PG_uncompressed) { >>> + page->flags &= ~PG_uncompressed; >>> + spin_unlock(&pool->lock); >>> + pool->ops->evict(pool, encode_handle(zhdr, FULL)); >>> + __free_page(page); >>> + return 0; >> >> again, don't be redundant. change the function to handle full-sized >> pages, don't repeat the function in an if() block for a special case. > > Well, this case is a little tricky. How to process a zbud page in > zbud_reclaim_page() is defined basing on the assumption there is a > zhdr at the beginning of the page. What can be done here IMV is either > of the following: aha, this is why you used the page flag. > * add a constant magic number to zhdr and check for it, if the check > fails, it is a type FULL page > * add a CRC field to zhdr, if CRC check over assumed zhdr fails, it > is a type FULL page neither of those; you can't guarantee the magic number won't naturally occur in a page. > * use a field from struct page to indicate its type sure, you could use a pre-existing field from struct page, like the page->private field. > > The last option still looks better to me. > > ~vitaly -- 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: email@kvack.org