zram: mark incompressible page as ZRAM_HUGE

Mark incompressible pages so that we could investigate who is the owner
of the incompressible pages once the page is swapped out via using
upcoming zram memory tracker feature.

With it, we could prevent such pages to be swapped out by using mlock.
Otherwise we might remove them.

This patch exposes new stat for huge pages via mm_stat.

Link: http://lkml.kernel.org/r/20180416090946.63057-3-minchan@kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 257e65714c6a216f3fce9ebce7398eb821f96176..78db38d02bc9a27a7ffd936ef857455960fe7459 100644 (file)
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -218,6 +218,7 @@ line of text and contains the following stats separated by whitespace:
  same_pages       the number of same element filled pages written to this disk.
                   No memory is allocated for such pages.
  pages_compacted  the number of pages freed during compaction
+ huge_pages      the number of incompressible pages
 
 9) Deactivate:
        swapoff /dev/zram0

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 18dadeab775b91cd2e73294094ab6805ffe4779a..777fb3339f598e698cdee580735770ec4a2dd611 100644 (file)
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -729,14 +729,15 @@ static ssize_t mm_stat_show(struct device *dev,
        max_used = atomic_long_read(&zram->stats.max_used_pages);
 
        ret = scnprintf(buf, PAGE_SIZE,
-                       "%8llu %8llu %8llu %8lu %8ld %8llu %8lu\n",
+                       "%8llu %8llu %8llu %8lu %8ld %8llu %8lu %8llu\n",
                        orig_size << PAGE_SHIFT,
                        (u64)atomic64_read(&zram->stats.compr_data_size),
                        mem_used << PAGE_SHIFT,
                        zram->limit_pages << PAGE_SHIFT,
                        max_used << PAGE_SHIFT,
                        (u64)atomic64_read(&zram->stats.same_pages),
-                       pool_stats.pages_compacted);
+                       pool_stats.pages_compacted,
+                       (u64)atomic64_read(&zram->stats.huge_pages));
        up_read(&zram->init_lock);
 
        return ret;
@@ -805,6 +806,11 @@ static void zram_free_page(struct zram *zram, size_t index)
 {
        unsigned long handle;
 
+       if (zram_test_flag(zram, index, ZRAM_HUGE)) {
+               zram_clear_flag(zram, index, ZRAM_HUGE);
+               atomic64_dec(&zram->stats.huge_pages);
+       }
+
        if (zram_wb_enabled(zram) && zram_test_flag(zram, index, ZRAM_WB)) {
                zram_wb_clear(zram, index);
                atomic64_dec(&zram->stats.pages_stored);
@@ -973,6 +979,7 @@ compress_again:
        }
 
        if (unlikely(comp_len >= huge_class_size)) {
+               comp_len = PAGE_SIZE;
                if (zram_wb_enabled(zram) && allow_wb) {
                        zcomp_stream_put(zram->comp);
                        ret = write_to_bdev(zram, bvec, index, bio, &element);
@@ -984,7 +991,6 @@ compress_again:
                        allow_wb = false;
                        goto compress_again;
                }
-               comp_len = PAGE_SIZE;
        }
 
        /*
@@ -1046,6 +1052,11 @@ out:
        zram_slot_lock(zram, index);
        zram_free_page(zram, index);
 
+       if (comp_len == PAGE_SIZE) {
+               zram_set_flag(zram, index, ZRAM_HUGE);
+               atomic64_inc(&zram->stats.huge_pages);
+       }
+
        if (flags) {
                zram_set_flag(zram, index, flags);
                zram_set_element(zram, index, element);

diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 8d8959ceabd1cd8cc8c221b30b77c0f3617aa885..ff0547bdb58678e9ee7dd4fc71407b8610d5bb32 100644 (file)
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -47,6 +47,7 @@ enum zram_pageflags {
        ZRAM_LOCK = ZRAM_FLAG_SHIFT,
        ZRAM_SAME,      /* Page consists the same element */
        ZRAM_WB,        /* page is stored on backing_device */
+       ZRAM_HUGE,      /* Incompressible page */
 
        __NR_ZRAM_PAGEFLAGS,
 };
@@ -71,6 +72,7 @@ struct zram_stats {
        atomic64_t invalid_io;  /* non-page-aligned I/O requests */
        atomic64_t notify_free; /* no. of swap slot free notifications */
        atomic64_t same_pages;          /* no. of same element filled pages */
+       atomic64_t huge_pages;          /* no. of huge pages */
        atomic64_t pages_stored;        /* no. of pages currently stored */
        atomic_long_t max_used_pages;   /* no. of maximum pages stored */
        atomic64_t writestall;          /* no. of write slow paths */