From 3de738cd30306f754ea35d35b5dad29fdbec84c9 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Wed, 30 Jan 2013 11:41:41 +0900 Subject: [PATCH] zram: give up lazy initialization of zram metadata 1) User of zram normally do mkfs.xxx or mkswap before using the zram block device(ex, normally, do it at booting time) It ends up allocating such metadata of zram before real usage so benefit of lazy initialzation would be mitigated. 2) Some user want to use zram when memory pressure is high.(ie, load zram dynamically, NOT booting time). It does make sense because people don't want to waste memory until memory pressure is high(ie, where zram is really helpful time). In this case, lazy initialzation could be failed easily because we will use GFP_NOIO instead of GFP_KERNEL for avoiding deadlock. So the benefit of lazy initialzation would be mitigated, too. 3) Metadata overhead is not critical and Nitin has a plan to diet it. 4K : 12 byte(64bit machine) -> 64G : 192M so 0.3% isn't big overhead If insane user use such big zram device up to 20, it could consume 6% of ram but efficieny of zram will cover the waste. So this patch gives up lazy initialization and instead we initialize metadata at disksize setting time. Acked-by: Jerome Marchand Acked-by: Nitin Gupta Signed-off-by: Minchan Kim Signed-off-by: Greg Kroah-Hartman --- drivers/staging/zram/zram_drv.c | 20 ++++---------------- drivers/staging/zram/zram_sysfs.c | 1 + 2 files changed, 5 insertions(+), 16 deletions(-) diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c index 1114cadfb960..85055c4fc2f2 100644 --- a/drivers/staging/zram/zram_drv.c +++ b/drivers/staging/zram/zram_drv.c @@ -442,16 +442,13 @@ static void zram_make_request(struct request_queue *queue, struct bio *bio) { struct zram *zram = queue->queuedata; - if (unlikely(!zram->init_done) && zram_init_device(zram)) - goto error; - down_read(&zram->init_lock); if (unlikely(!zram->init_done)) - goto error_unlock; + goto error; if (!valid_io_request(zram, bio)) { zram_stat64_inc(zram, &zram->stats.invalid_io); - goto error_unlock; + goto error; } __zram_make_request(zram, bio, bio_data_dir(bio)); @@ -459,9 +456,8 @@ static void zram_make_request(struct request_queue *queue, struct bio *bio) return; -error_unlock: - up_read(&zram->init_lock); error: + up_read(&zram->init_lock); bio_io_error(bio); } @@ -510,18 +506,12 @@ void zram_reset_device(struct zram *zram) up_write(&zram->init_lock); } +/* zram->init_lock should be held */ int zram_init_device(struct zram *zram) { int ret; size_t num_pages; - down_write(&zram->init_lock); - - if (zram->init_done) { - up_write(&zram->init_lock); - return 0; - } - if (zram->disksize > 2 * (totalram_pages << PAGE_SHIFT)) { pr_info( "There is little point creating a zram of greater than " @@ -570,7 +560,6 @@ int zram_init_device(struct zram *zram) } zram->init_done = 1; - up_write(&zram->init_lock); pr_debug("Initialization done!\n"); return 0; @@ -580,7 +569,6 @@ fail_no_table: zram->disksize = 0; fail: __zram_reset_device(zram); - up_write(&zram->init_lock); pr_err("Initialization failed: err=%d\n", ret); return ret; } diff --git a/drivers/staging/zram/zram_sysfs.c b/drivers/staging/zram/zram_sysfs.c index 4143af9fcc1b..369db1250f96 100644 --- a/drivers/staging/zram/zram_sysfs.c +++ b/drivers/staging/zram/zram_sysfs.c @@ -71,6 +71,7 @@ static ssize_t disksize_store(struct device *dev, zram->disksize = PAGE_ALIGN(disksize); set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT); + zram_init_device(zram); up_write(&zram->init_lock); return len; -- 2.20.1