From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9E9D3C4332F for ; Fri, 4 Nov 2022 17:53:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231869AbiKDRx3 (ORCPT ); Fri, 4 Nov 2022 13:53:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57990 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231634AbiKDRx0 (ORCPT ); Fri, 4 Nov 2022 13:53:26 -0400 Received: from mail-pl1-x630.google.com (mail-pl1-x630.google.com [IPv6:2607:f8b0:4864:20::630]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 307DA13F58 for ; Fri, 4 Nov 2022 10:53:24 -0700 (PDT) Received: by mail-pl1-x630.google.com with SMTP id l2so5539387pld.13 for ; Fri, 04 Nov 2022 10:53:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:from:to:cc:subject:date:message-id :reply-to; bh=5AYqS6mUkjpXYu0T8n2KAq9xhXXH9ady33cw5jnMQfc=; b=oa0bWEELOkYXMyGM8Nr2LpiqMV8AeIGsNwMsA2/belHZtqm8lU2Vm32X9ex8K7R/jZ a71lzul/ITSf8L72il2yLGy2PVhdERNYB/kU8imcv8WCgAfsx+IrgA3vV9hngSoZN2jh Zgse9vFoPwGL962j9enmfSnr+nhUhxfiyjakBnRLBx3psXf8CYsPYUWnledbA98wrgu8 cWwYX76ZgWV9NRCgqKsrGFa5PnjbM+oZiVMfkWVxLyo3S4VHlU1BW7MTx67QCvIUDwzv 4hvgrubfRR7dVV6SlYAd5/e+uzbashuY0FrbXSpe+FrB7lB4HubkdldpQM/RocPWpl1q s4jA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:sender:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=5AYqS6mUkjpXYu0T8n2KAq9xhXXH9ady33cw5jnMQfc=; b=Cymb4srlBJgguP/buINtxr6lrxqnDi4JHGpB8qN8rCR/m15KWsssq1p2jCBfLRxERM ru1ksKvmO0DwqZ3zzImUgkwqIy+sk6GrPWg9FAUGfPU305TB/ucO0dXcg4ydWbX0n45M LhObXMFMS/L6Nc1xRzhhRBHQB1VT/YS7t2HBAXtNUafXjJd0XZNpR1t1TYG7xzqGpLMV Ls7Go9F0p+4vpEmBT8T47FBg3jXrUdctFJylzZLzgzmMvoW4zqUl+iS6XjRj4Gu6HBCf fU4UwJDFWGUB7Xc67LlocA7r/p9VpfHFfE7B2Ybhf9bFnL0IKMt2Cx+q3di1qn8YI59b WTyQ== X-Gm-Message-State: ACrzQf0xj4U3pVpTZGONyFdG9OcQ1AMFcc0Z+UloVd3jcZ5S0MQuJ6of 1rg6UsINOB9xO90I8Bc6wP4= X-Google-Smtp-Source: AMsMyM6Yx44eGHHswjMF/T+vbjCAyA/4tua1IM0bZYF1atgKJLGGcH6VWOBtIMuQ3FU39KesOAAjyw== X-Received: by 2002:a17:903:2352:b0:186:aaed:e7b8 with SMTP id c18-20020a170903235200b00186aaede7b8mr35944162plh.47.1667584403403; Fri, 04 Nov 2022 10:53:23 -0700 (PDT) Received: from google.com ([2620:15c:211:201:755f:cdcb:1bd8:5ad8]) by smtp.gmail.com with ESMTPSA id a9-20020a170902ecc900b001886ff82680sm12698plh.127.2022.11.04.10.53.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Nov 2022 10:53:22 -0700 (PDT) Sender: Minchan Kim Date: Fri, 4 Nov 2022 10:53:21 -0700 From: Minchan Kim To: Sergey Senozhatsky Cc: Andrew Morton , Nitin Gupta , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCHv4 4/9] zram: Introduce recompress sysfs knob Message-ID: References: <20221018045533.2396670-1-senozhatsky@chromium.org> <20221018045533.2396670-5-senozhatsky@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 04, 2022 at 04:12:13PM +0900, Sergey Senozhatsky wrote: > On (22/11/04 12:48), Sergey Senozhatsky wrote: > > > read_block_state > > > zram_algo_idx(zram, index) > 0 ? 'r' : '.'); > > > > > > zram_read_from_zpool > > > if (zram_algo_idx(zram, idx) != 0) > > > idx = 1; > > > > As an idea, maybe we can store everything re-compression related > > in a dedicated meta field? SKIP flag, algorithm ID, etc. > > That's just an idea. > > Something like this > > --- > diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h > index bdfc9bf0bdd5..c011d0f145f6 100644 > --- a/drivers/block/zram/zram_drv.h > +++ b/drivers/block/zram/zram_drv.h > @@ -49,8 +49,6 @@ enum zram_pageflags { > ZRAM_UNDER_WB, /* page is under writeback */ > ZRAM_HUGE, /* Incompressible page */ > ZRAM_IDLE, /* not accessed page since last idle marking */ > - ZRAM_RECOMP, /* page was recompressed */ > - ZRAM_RECOMP_SKIP, /* secondary algorithm cannot compress this page */ > > __NR_ZRAM_PAGEFLAGS, > }; > @@ -64,6 +62,11 @@ struct zram_table_entry { > unsigned long element; > }; > unsigned long flags; > +#ifdef CONFIG_ZRAM_MULTI_COMP > + unsigned int incompressible:1; > + unsigned int priority:2; > +#endif > + > #ifdef CONFIG_ZRAM_MEMORY_TRACKING > ktime_t ac_time; > #endif > --- > > The reason I'm thinking about it is that we have flags bits that are > used only when particular .config options are enabled. Without those > options we just waste bits. > > Recompression is one such thing. Another one is writeback. > > --- > diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h > index c011d0f145f6..7076ec209e79 100644 > --- a/drivers/block/zram/zram_drv.h > +++ b/drivers/block/zram/zram_drv.h > @@ -45,8 +45,6 @@ enum zram_pageflags { > /* zram slot is locked */ > ZRAM_LOCK = ZRAM_FLAG_SHIFT, > ZRAM_SAME, /* Page consists the same element */ > - ZRAM_WB, /* page is stored on backing_device */ > - ZRAM_UNDER_WB, /* page is under writeback */ > ZRAM_HUGE, /* Incompressible page */ > ZRAM_IDLE, /* not accessed page since last idle marking */ > > @@ -68,6 +66,8 @@ struct zram_table_entry { > #endif > > #ifdef CONFIG_ZRAM_MEMORY_TRACKING > + unsigned int under_writeback:1; > + unsigned int written_back:1; > ktime_t ac_time; > #endif > }; > --- > > So we can use ->flags only for things that are independent of .config Couldn't we move them into a dedicated field to introduce one more field overhead in the meta area when we run out the extra field in the flag? So I'd like to squeeze the bits into flag.