From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751705AbbIOFn1 (ORCPT ); Tue, 15 Sep 2015 01:43:27 -0400 Received: from mail-io0-f181.google.com ([209.85.223.181]:35433 "EHLO mail-io0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751005AbbIOFn0 (ORCPT ); Tue, 15 Sep 2015 01:43:26 -0400 MIME-Version: 1.0 In-Reply-To: <20150914155036.7c90a8e313cb0ed4d4857934@gmail.com> References: <20150914154901.92c5b7b24e15f04d8204de18@gmail.com> <20150914155036.7c90a8e313cb0ed4d4857934@gmail.com> From: Dan Streetman Date: Tue, 15 Sep 2015 01:42:46 -0400 X-Google-Sender-Auth: RFCi1IM9w8IIVsZtA2vrl5nhkC0 Message-ID: Subject: Re: [PATCH 1/3] zram: make max_zpage_size configurable To: Vitaly Wool Cc: Minchan Kim , Sergey Senozhatsky , linux-kernel , Linux-MM Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 14, 2015 at 9:50 AM, Vitaly Wool wrote: > It makes sense to have control over what compression ratios are > ok to store pages uncompressed and what not. Moreover, if we end > up using zbud allocator for zram, any attempt to allocate a whole > page will fail, so we may want to avoid this as much as possible. Well, zram explicitly expects to be able to store PAGE_SIZE'd objects: if (unlikely(clen > max_zpage_size)) clen = PAGE_SIZE; handle = zs_malloc(meta->mem_pool, clen); so the max_zpage_size doesn't prevent zram from trying to store the page in zsmalloc/zbud/whatever; instead, if the compressed page is larger than max_zpage_size, it just stores it uncompressed (as a side note, I'm not quite sure what the benefit of not storing in compressed form any pages that compress to between 3/4 and 1 page is...I suppose the decompression time is skipped, but it also wastes space...i would just make max_zpage_size == PAGE_SIZE). but zbud can't store a PAGE_SIZE'd object. so the behavior would change. The current behavior is: compressed page <= max_zpage_size : stored compressed compressed page > max_zpage_size : stored uncompressed new behavior: compressed page <= max_zpage_size : stored compressed compressed page > max_zpage_size : zram write fails to do this right, I think you have to change zbud to be able to store PAGE_SIZE'd objects. That should be doable, I think you can just the page->lru to store it in the zbud lru, and use a page flag to indicate it's uncompressed, full PAGE_SIZE page, or something like that. But without the ability to store full pages, zbud won't work well with zram. > > So, let's have max_zpage_size configurable as a module parameter. > > Signed-off-by: Vitaly Wool > --- > drivers/block/zram/zram_drv.c | 13 +++++++++++++ > drivers/block/zram/zram_drv.h | 16 ---------------- > 2 files changed, 13 insertions(+), 16 deletions(-) > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > index 9fa15bb..6d9f1d1 100644 > --- a/drivers/block/zram/zram_drv.c > +++ b/drivers/block/zram/zram_drv.c > @@ -42,6 +42,7 @@ static const char *default_compressor = "lzo"; > > /* Module params (documentation at end) */ > static unsigned int num_devices = 1; > +static size_t max_zpage_size = PAGE_SIZE / 4 * 3; > > static inline void deprecated_attr_warn(const char *name) > { > @@ -1411,6 +1412,16 @@ static int __init zram_init(void) > return ret; > } > > + /* > + * max_zpage_size must be less than or equal to: > + * ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would > + * always return failure. > + */ > + if (max_zpage_size > PAGE_SIZE) { > + pr_err("Invalid max_zpage_size %ld\n", max_zpage_size); > + return -EINVAL; > + } > + > zram_major = register_blkdev(0, "zram"); > if (zram_major <= 0) { > pr_err("Unable to get major number\n"); > @@ -1444,6 +1455,8 @@ module_exit(zram_exit); > > module_param(num_devices, uint, 0); > MODULE_PARM_DESC(num_devices, "Number of pre-created zram devices"); > +module_param(max_zpage_size, ulong, 0); > +MODULE_PARM_DESC(max_zpage_size, "Threshold for storing compressed pages"); > > MODULE_LICENSE("Dual BSD/GPL"); > MODULE_AUTHOR("Nitin Gupta "); > diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h > index 8e92339..3a29c33 100644 > --- a/drivers/block/zram/zram_drv.h > +++ b/drivers/block/zram/zram_drv.h > @@ -20,22 +20,6 @@ > > #include "zcomp.h" > > -/*-- Configurable parameters */ > - > -/* > - * Pages that compress to size greater than this are stored > - * uncompressed in memory. > - */ > -static const size_t max_zpage_size = PAGE_SIZE / 4 * 3; > - > -/* > - * NOTE: max_zpage_size must be less than or equal to: > - * ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would > - * always return failure. > - */ > - > -/*-- End of configurable params */ > - > #define SECTOR_SHIFT 9 > #define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT) > #define SECTORS_PER_PAGE (1 << SECTORS_PER_PAGE_SHIFT) > -- > 1.9.1 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f182.google.com (mail-io0-f182.google.com [209.85.223.182]) by kanga.kvack.org (Postfix) with ESMTP id 8C54A6B0253 for ; Tue, 15 Sep 2015 01:43:26 -0400 (EDT) Received: by ioii196 with SMTP id i196so190704214ioi.3 for ; Mon, 14 Sep 2015 22:43:26 -0700 (PDT) Received: from mail-io0-x234.google.com (mail-io0-x234.google.com. [2607:f8b0:4001:c06::234]) by mx.google.com with ESMTPS id j202si11829809ioj.32.2015.09.14.22.43.25 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 14 Sep 2015 22:43:25 -0700 (PDT) Received: by ioii196 with SMTP id i196so190704110ioi.3 for ; Mon, 14 Sep 2015 22:43:25 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20150914155036.7c90a8e313cb0ed4d4857934@gmail.com> References: <20150914154901.92c5b7b24e15f04d8204de18@gmail.com> <20150914155036.7c90a8e313cb0ed4d4857934@gmail.com> From: Dan Streetman Date: Tue, 15 Sep 2015 01:42:46 -0400 Message-ID: Subject: Re: [PATCH 1/3] zram: make max_zpage_size configurable Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Vitaly Wool Cc: Minchan Kim , Sergey Senozhatsky , linux-kernel , Linux-MM On Mon, Sep 14, 2015 at 9:50 AM, Vitaly Wool wrote: > It makes sense to have control over what compression ratios are > ok to store pages uncompressed and what not. Moreover, if we end > up using zbud allocator for zram, any attempt to allocate a whole > page will fail, so we may want to avoid this as much as possible. Well, zram explicitly expects to be able to store PAGE_SIZE'd objects: if (unlikely(clen > max_zpage_size)) clen = PAGE_SIZE; handle = zs_malloc(meta->mem_pool, clen); so the max_zpage_size doesn't prevent zram from trying to store the page in zsmalloc/zbud/whatever; instead, if the compressed page is larger than max_zpage_size, it just stores it uncompressed (as a side note, I'm not quite sure what the benefit of not storing in compressed form any pages that compress to between 3/4 and 1 page is...I suppose the decompression time is skipped, but it also wastes space...i would just make max_zpage_size == PAGE_SIZE). but zbud can't store a PAGE_SIZE'd object. so the behavior would change. The current behavior is: compressed page <= max_zpage_size : stored compressed compressed page > max_zpage_size : stored uncompressed new behavior: compressed page <= max_zpage_size : stored compressed compressed page > max_zpage_size : zram write fails to do this right, I think you have to change zbud to be able to store PAGE_SIZE'd objects. That should be doable, I think you can just the page->lru to store it in the zbud lru, and use a page flag to indicate it's uncompressed, full PAGE_SIZE page, or something like that. But without the ability to store full pages, zbud won't work well with zram. > > So, let's have max_zpage_size configurable as a module parameter. > > Signed-off-by: Vitaly Wool > --- > drivers/block/zram/zram_drv.c | 13 +++++++++++++ > drivers/block/zram/zram_drv.h | 16 ---------------- > 2 files changed, 13 insertions(+), 16 deletions(-) > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > index 9fa15bb..6d9f1d1 100644 > --- a/drivers/block/zram/zram_drv.c > +++ b/drivers/block/zram/zram_drv.c > @@ -42,6 +42,7 @@ static const char *default_compressor = "lzo"; > > /* Module params (documentation at end) */ > static unsigned int num_devices = 1; > +static size_t max_zpage_size = PAGE_SIZE / 4 * 3; > > static inline void deprecated_attr_warn(const char *name) > { > @@ -1411,6 +1412,16 @@ static int __init zram_init(void) > return ret; > } > > + /* > + * max_zpage_size must be less than or equal to: > + * ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would > + * always return failure. > + */ > + if (max_zpage_size > PAGE_SIZE) { > + pr_err("Invalid max_zpage_size %ld\n", max_zpage_size); > + return -EINVAL; > + } > + > zram_major = register_blkdev(0, "zram"); > if (zram_major <= 0) { > pr_err("Unable to get major number\n"); > @@ -1444,6 +1455,8 @@ module_exit(zram_exit); > > module_param(num_devices, uint, 0); > MODULE_PARM_DESC(num_devices, "Number of pre-created zram devices"); > +module_param(max_zpage_size, ulong, 0); > +MODULE_PARM_DESC(max_zpage_size, "Threshold for storing compressed pages"); > > MODULE_LICENSE("Dual BSD/GPL"); > MODULE_AUTHOR("Nitin Gupta "); > diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h > index 8e92339..3a29c33 100644 > --- a/drivers/block/zram/zram_drv.h > +++ b/drivers/block/zram/zram_drv.h > @@ -20,22 +20,6 @@ > > #include "zcomp.h" > > -/*-- Configurable parameters */ > - > -/* > - * Pages that compress to size greater than this are stored > - * uncompressed in memory. > - */ > -static const size_t max_zpage_size = PAGE_SIZE / 4 * 3; > - > -/* > - * NOTE: max_zpage_size must be less than or equal to: > - * ZS_MAX_ALLOC_SIZE. Otherwise, zs_malloc() would > - * always return failure. > - */ > - > -/*-- End of configurable params */ > - > #define SECTOR_SHIFT 9 > #define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT) > #define SECTORS_PER_PAGE (1 << SECTORS_PER_PAGE_SHIFT) > -- > 1.9.1 -- 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