linux-kernel - [PATCH] zram: add limit to recompression

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Message-ID: <20240329090700.2799449-1-senozhatsky@chromium.org>
Date: Fri, 29 Mar 2024 18:06:44 +0900
From: Sergey Senozhatsky <senozhatsky@...omium.org>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan@...nel.org>
Cc: Brian Geffon <bgeffon@...gle.com>,
	linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org,
	Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: [PATCH] zram: add limit to recompression

Introduce "max_pages" param to recompression device attribute
which sets the upper limit on the number of entries (pages) zram
attempts to recompress.

Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
---
 Documentation/admin-guide/blockdev/zram.rst |  5 +++++
 drivers/block/zram/zram_drv.c               | 18 ++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/Documentation/admin-guide/blockdev/zram.rst b/Documentation/admin-guide/blockdev/zram.rst
index ee2b0030d416..091e8bb38887 100644
--- a/Documentation/admin-guide/blockdev/zram.rst
+++ b/Documentation/admin-guide/blockdev/zram.rst
@@ -466,6 +466,11 @@ of equal or greater size:::
 	#recompress idle pages larger than 2000 bytes
 	echo "type=idle threshold=2000" > /sys/block/zramX/recompress
 
+It is also possible to limit the number of pages zram re-compression will
+attempt to recompress:::
+
+	echo "type=huge_idle max_pages=42" > /sys/block/zramX/recompress
+
 Recompression of idle pages requires memory tracking.
 
 During re-compression for every page, that matches re-compression criteria,
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index f0639df6cd18..a97986c52476 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -1710,6 +1710,7 @@ static ssize_t recompress_store(struct device *dev,
 	struct zram *zram = dev_to_zram(dev);
 	unsigned long nr_pages = zram->disksize >> PAGE_SHIFT;
 	char *args, *param, *val, *algo = NULL;
+	u64 recomp_limit = ULLONG_MAX;
 	u32 mode = 0, threshold = 0;
 	unsigned long index;
 	struct page *page;
@@ -1732,6 +1733,17 @@ static ssize_t recompress_store(struct device *dev,
 			continue;
 		}
 
+		if (!strcmp(param, "max_pages")) {
+			/*
+			 * Limit the number of entries (pages) we attempt to
+			 * recompress.
+			 */
+			ret = kstrtoull(val, 10, &recomp_limit);
+			if (ret)
+				return ret;
+			continue;
+		}
+
 		if (!strcmp(param, "threshold")) {
 			/*
 			 * We will re-compress only idle objects equal or
@@ -1788,6 +1800,9 @@ static ssize_t recompress_store(struct device *dev,
 	for (index = 0; index < nr_pages; index++) {
 		int err = 0;
 
+		if (!recomp_limit)
+			break;
+
 		zram_slot_lock(zram, index);
 
 		if (!zram_allocated(zram, index))
@@ -1816,6 +1831,9 @@ static ssize_t recompress_store(struct device *dev,
 			break;
 		}
 
+		if (recomp_limit > 0)
+			recomp_limit--;
+
 		cond_resched();
 	}
 
-- 
2.44.0.478.gd926399ef9-goog