linux-kernel - [PATCH v3 7/7] mm, slab: shorten kmalloc cache names for large sizes

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Date:   Wed, 18 Jul 2018 15:36:20 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, Roman Gushchin <guro@...com>,
        Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Christoph Lameter <cl@...ux.com>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH v3 7/7] mm, slab: shorten kmalloc cache names for large sizes

Kmalloc cache names can get quite long for large object sizes, when the sizes
are expressed in bytes. Use 'k' and 'M' prefixes to make the names as short
as possible e.g. in /proc/slabinfo. This works, as we mostly use power-of-two
sizes, with exceptions only below 1k.

Example: 'kmalloc-4194304' becomes 'kmalloc-4M'

Suggested-by: Matthew Wilcox <willy@...radead.org>
Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slab_common.c | 38 ++++++++++++++++++++++++++------------
 1 file changed, 26 insertions(+), 12 deletions(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index 614fb7ab8312..04d71ead7d12 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -1049,15 +1049,15 @@ const struct kmalloc_info_struct kmalloc_info[] __initconst = {
 	{"kmalloc-16",             16},		{"kmalloc-32",             32},
 	{"kmalloc-64",             64},		{"kmalloc-128",           128},
 	{"kmalloc-256",           256},		{"kmalloc-512",           512},
-	{"kmalloc-1024",         1024},		{"kmalloc-2048",         2048},
-	{"kmalloc-4096",         4096},		{"kmalloc-8192",         8192},
-	{"kmalloc-16384",       16384},		{"kmalloc-32768",       32768},
-	{"kmalloc-65536",       65536},		{"kmalloc-131072",     131072},
-	{"kmalloc-262144",     262144},		{"kmalloc-524288",     524288},
-	{"kmalloc-1048576",   1048576},		{"kmalloc-2097152",   2097152},
-	{"kmalloc-4194304",   4194304},		{"kmalloc-8388608",   8388608},
-	{"kmalloc-16777216", 16777216},		{"kmalloc-33554432", 33554432},
-	{"kmalloc-67108864", 67108864}
+	{"kmalloc-1k",           1024},		{"kmalloc-2k",           2048},
+	{"kmalloc-4k",           4096},		{"kmalloc-8k",           8192},
+	{"kmalloc-16k",         16384},		{"kmalloc-32k",         32768},
+	{"kmalloc-64k",         65536},		{"kmalloc-128k",       131072},
+	{"kmalloc-256k",       262144},		{"kmalloc-512k",       524288},
+	{"kmalloc-1M",        1048576},		{"kmalloc-2M",        2097152},
+	{"kmalloc-4M",        4194304},		{"kmalloc-8M",        8388608},
+	{"kmalloc-16M",      16777216},		{"kmalloc-32M",      33554432},
+	{"kmalloc-64M",      67108864}
 };
 
 /*
@@ -1107,6 +1107,21 @@ void __init setup_kmalloc_cache_index_table(void)
 	}
 }
 
+static const char *
+kmalloc_cache_name(const char *prefix, unsigned int size)
+{
+
+	static const char units[3] = "\0kM";
+	int idx = 0;
+
+	while (size >= 1024 && (size % 1024 == 0)) {
+		size /= 1024;
+		idx++;
+	}
+
+	return kasprintf(GFP_NOWAIT, "%s-%u%c", prefix, size, units[idx]);
+}
+
 static void __init
 new_kmalloc_cache(int idx, int type, slab_flags_t flags)
 {
@@ -1114,7 +1129,7 @@ new_kmalloc_cache(int idx, int type, slab_flags_t flags)
 
 	if (type == KMALLOC_RECLAIM) {
 		flags |= SLAB_RECLAIM_ACCOUNT;
-		name = kasprintf(GFP_NOWAIT, "kmalloc-rcl-%u",
+		name = kmalloc_cache_name("kmalloc-rcl",
 						kmalloc_info[idx].size);
 		BUG_ON(!name);
 	} else {
@@ -1163,8 +1178,7 @@ void __init create_kmalloc_caches(slab_flags_t flags)
 
 		if (s) {
 			unsigned int size = kmalloc_size(i);
-			char *n = kasprintf(GFP_NOWAIT,
-				 "dma-kmalloc-%u", size);
+			const char *n = kmalloc_cache_name("dma-kmalloc", size);
 
 			BUG_ON(!n);
 			kmalloc_caches[KMALLOC_DMA][i] = create_kmalloc_cache(
-- 
2.18.0