* [PATCH] Use ilog2() in fs/namespace.c @ 2007-12-14 17:51 Eric Dumazet 2007-12-21 10:29 ` Andrew Morton 0 siblings, 1 reply; 3+ messages in thread From: Eric Dumazet @ 2007-12-14 17:51 UTC (permalink / raw) To: Andrew Morton; +Cc: linux kernel, Al Viro [-- Attachment #1: Type: text/plain, Size: 154 bytes --] We can use ilog2() in fs/namespace.c to compute hash_bits and hash_mask at compile time, not runtime. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> [-- Attachment #2: namespace.patch --] [-- Type: text/plain, Size: 1416 bytes --] diff --git a/fs/namespace.c b/fs/namespace.c index 0608388..835f14a 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -25,6 +25,7 @@ #include <linux/security.h> #include <linux/mount.h> #include <linux/ramfs.h> +#include <linux/log2.h> #include <asm/uaccess.h> #include <asm/unistd.h> #include "pnode.h" @@ -36,7 +37,8 @@ __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); static int event; static struct list_head *mount_hashtable __read_mostly; -static int hash_mask __read_mostly, hash_bits __read_mostly; +#define hash_bits ilog2(PAGE_SIZE / sizeof(struct list_head)) +#define hash_mask ((1UL << hash_bits) - 1) static struct kmem_cache *mnt_cache __read_mostly; static struct rw_semaphore namespace_sem; @@ -1828,24 +1830,7 @@ void __init mnt_init(void) if (!mount_hashtable) panic("Failed to allocate mount hash table\n"); - /* - * Find the power-of-two list-heads that can fit into the allocation.. - * We don't guarantee that "sizeof(struct list_head)" is necessarily - * a power-of-two. - */ - nr_hash = PAGE_SIZE / sizeof(struct list_head); - hash_bits = 0; - do { - hash_bits++; - } while ((nr_hash >> hash_bits) != 0); - hash_bits--; - - /* - * Re-calculate the actual number of entries and the mask - * from the number of bits we can fit. - */ nr_hash = 1UL << hash_bits; - hash_mask = nr_hash - 1; printk("Mount-cache hash table entries: %d\n", nr_hash); ^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] Use ilog2() in fs/namespace.c 2007-12-14 17:51 [PATCH] Use ilog2() in fs/namespace.c Eric Dumazet @ 2007-12-21 10:29 ` Andrew Morton 2007-12-21 11:34 ` Eric Dumazet 0 siblings, 1 reply; 3+ messages in thread From: Andrew Morton @ 2007-12-21 10:29 UTC (permalink / raw) To: Eric Dumazet; +Cc: linux kernel, Al Viro On Fri, 14 Dec 2007 18:51:06 +0100 Eric Dumazet <dada1@cosmosbay.com> wrote: > We can use ilog2() in fs/namespace.c to compute hash_bits and hash_mask at > compile time, not runtime. Well noted. > [namespace.patch text/plain (1.4KB)] argh. (save-as, read, copy-paste, s/^/> /g) > --- a/fs/namespace.c > +++ b/fs/namespace.c > @@ -25,6 +25,7 @@ > #include <linux/security.h> > #include <linux/mount.h> > #include <linux/ramfs.h> > +#include <linux/log2.h> > #include <asm/uaccess.h> > #include <asm/unistd.h> > #include "pnode.h" > @@ -36,7 +37,8 @@ __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); > static int event; > > static struct list_head *mount_hashtable __read_mostly; > -static int hash_mask __read_mostly, hash_bits __read_mostly; > +#define hash_bits ilog2(PAGE_SIZE / sizeof(struct list_head)) > +#define hash_mask ((1UL << hash_bits) - 1) > static struct kmem_cache *mnt_cache __read_mostly; > static struct rw_semaphore namespace_sem; > > @@ -1828,24 +1830,7 @@ void __init mnt_init(void) > if (!mount_hashtable) > panic("Failed to allocate mount hash table\n"); > > - /* > - * Find the power-of-two list-heads that can fit into the allocation.. > - * We don't guarantee that "sizeof(struct list_head)" is necessarily > - * a power-of-two. > - */ > - nr_hash = PAGE_SIZE / sizeof(struct list_head); > - hash_bits = 0; > - do { > - hash_bits++; > - } while ((nr_hash >> hash_bits) != 0); > - hash_bits--; > - > - /* > - * Re-calculate the actual number of entries and the mask > - * from the number of bits we can fit. > - */ > nr_hash = 1UL << hash_bits; > - hash_mask = nr_hash - 1; > > printk("Mount-cache hash table entries: %d\n", nr_hash); Those #defines you now have there are foul. Please, when there's a choice between doing it minimally and doing it right, let's do it right? Look what we can now do: --- a/fs/namespace.c~use-ilog2-in-fs-namespacec-fix +++ a/fs/namespace.c @@ -31,14 +31,15 @@ #include "pnode.h" #include "internal.h" +#define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) +#define HASH_SIZE (1UL << HASH_SHIFT) + /* spinlock for vfsmount related operations, inplace of dcache_lock */ __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); static int event; static struct list_head *mount_hashtable __read_mostly; -#define hash_bits ilog2(PAGE_SIZE / sizeof(struct list_head)) -#define hash_mask ((1UL << hash_bits) - 1) static struct kmem_cache *mnt_cache __read_mostly; static struct rw_semaphore namespace_sem; @@ -50,8 +51,8 @@ static inline unsigned long hash(struct { unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); tmp += ((unsigned long)dentry / L1_CACHE_BYTES); - tmp = tmp + (tmp >> hash_bits); - return tmp & hash_mask; + tmp = tmp + (tmp >> HASH_SHIFT); + return tmp & (HASH_SIZE - 1); } struct vfsmount *alloc_vfsmnt(const char *name) @@ -1815,9 +1816,7 @@ static void __init init_mount_tree(void) void __init mnt_init(void) { - struct list_head *d; - unsigned int nr_hash; - int i; + unsigned u; int err; init_rwsem(&namespace_sem); @@ -1830,18 +1829,11 @@ void __init mnt_init(void) if (!mount_hashtable) panic("Failed to allocate mount hash table\n"); - nr_hash = 1UL << hash_bits; + printk("Mount-cache hash table entries: %lu\n", HASH_SIZE); - printk("Mount-cache hash table entries: %d\n", nr_hash); + for (u = 0; u < HASH_SIZE; u++) + INIT_LIST_HEAD(&mount_hashtable[u]); - /* And initialize the newly allocated array */ - d = mount_hashtable; - i = nr_hash; - do { - INIT_LIST_HEAD(d); - d++; - i--; - } while (i); err = sysfs_init(); if (err) printk(KERN_WARNING "%s: sysfs_init error: %d\n", _ ^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] Use ilog2() in fs/namespace.c 2007-12-21 10:29 ` Andrew Morton @ 2007-12-21 11:34 ` Eric Dumazet 0 siblings, 0 replies; 3+ messages in thread From: Eric Dumazet @ 2007-12-21 11:34 UTC (permalink / raw) To: Andrew Morton; +Cc: linux kernel, Al Viro On Fri, 21 Dec 2007 02:29:12 -0800 Andrew Morton <akpm@linux-foundation.org> wrote: > On Fri, 14 Dec 2007 18:51:06 +0100 Eric Dumazet <dada1@cosmosbay.com> wrote: > > > We can use ilog2() in fs/namespace.c to compute hash_bits and hash_mask at > > compile time, not runtime. > > Well noted. > > > [namespace.patch text/plain (1.4KB)] > > argh. (save-as, read, copy-paste, s/^/> /g) > > > --- a/fs/namespace.c > > +++ b/fs/namespace.c > > @@ -25,6 +25,7 @@ > > #include <linux/security.h> > > #include <linux/mount.h> > > #include <linux/ramfs.h> > > +#include <linux/log2.h> > > #include <asm/uaccess.h> > > #include <asm/unistd.h> > > #include "pnode.h" > > @@ -36,7 +37,8 @@ __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); > > static int event; > > > > static struct list_head *mount_hashtable __read_mostly; > > -static int hash_mask __read_mostly, hash_bits __read_mostly; > > +#define hash_bits ilog2(PAGE_SIZE / sizeof(struct list_head)) > > +#define hash_mask ((1UL << hash_bits) - 1) > > static struct kmem_cache *mnt_cache __read_mostly; > > static struct rw_semaphore namespace_sem; > > > > @@ -1828,24 +1830,7 @@ void __init mnt_init(void) > > if (!mount_hashtable) > > panic("Failed to allocate mount hash table\n"); > > > > - /* > > - * Find the power-of-two list-heads that can fit into the allocation.. > > - * We don't guarantee that "sizeof(struct list_head)" is necessarily > > - * a power-of-two. > > - */ > > - nr_hash = PAGE_SIZE / sizeof(struct list_head); > > - hash_bits = 0; > > - do { > > - hash_bits++; > > - } while ((nr_hash >> hash_bits) != 0); > > - hash_bits--; > > - > > - /* > > - * Re-calculate the actual number of entries and the mask > > - * from the number of bits we can fit. > > - */ > > nr_hash = 1UL << hash_bits; > > - hash_mask = nr_hash - 1; > > > > printk("Mount-cache hash table entries: %d\n", nr_hash); > > Those #defines you now have there are foul. Please, when there's a choice > between doing it minimally and doing it right, let's do it right? > Indeed ! Thanks Andrew for taking the time and fixing my lazyness :( Your version is much cleaner of course. > Look what we can now do: > > > --- a/fs/namespace.c~use-ilog2-in-fs-namespacec-fix > +++ a/fs/namespace.c > @@ -31,14 +31,15 @@ > #include "pnode.h" > #include "internal.h" > > +#define HASH_SHIFT ilog2(PAGE_SIZE / sizeof(struct list_head)) > +#define HASH_SIZE (1UL << HASH_SHIFT) > + > /* spinlock for vfsmount related operations, inplace of dcache_lock */ > __cacheline_aligned_in_smp DEFINE_SPINLOCK(vfsmount_lock); > > static int event; > > static struct list_head *mount_hashtable __read_mostly; > -#define hash_bits ilog2(PAGE_SIZE / sizeof(struct list_head)) > -#define hash_mask ((1UL << hash_bits) - 1) > static struct kmem_cache *mnt_cache __read_mostly; > static struct rw_semaphore namespace_sem; > > @@ -50,8 +51,8 @@ static inline unsigned long hash(struct > { > unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); > tmp += ((unsigned long)dentry / L1_CACHE_BYTES); > - tmp = tmp + (tmp >> hash_bits); > - return tmp & hash_mask; > + tmp = tmp + (tmp >> HASH_SHIFT); > + return tmp & (HASH_SIZE - 1); > } > > struct vfsmount *alloc_vfsmnt(const char *name) > @@ -1815,9 +1816,7 @@ static void __init init_mount_tree(void) > > void __init mnt_init(void) > { > - struct list_head *d; > - unsigned int nr_hash; > - int i; > + unsigned u; > int err; > > init_rwsem(&namespace_sem); > @@ -1830,18 +1829,11 @@ void __init mnt_init(void) > if (!mount_hashtable) > panic("Failed to allocate mount hash table\n"); > > - nr_hash = 1UL << hash_bits; > + printk("Mount-cache hash table entries: %lu\n", HASH_SIZE); > > - printk("Mount-cache hash table entries: %d\n", nr_hash); > + for (u = 0; u < HASH_SIZE; u++) > + INIT_LIST_HEAD(&mount_hashtable[u]); > > - /* And initialize the newly allocated array */ > - d = mount_hashtable; > - i = nr_hash; > - do { > - INIT_LIST_HEAD(d); > - d++; > - i--; > - } while (i); > err = sysfs_init(); > if (err) > printk(KERN_WARNING "%s: sysfs_init error: %d\n", > _ > ^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2007-12-21 11:35 UTC | newest] Thread overview: 3+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2007-12-14 17:51 [PATCH] Use ilog2() in fs/namespace.c Eric Dumazet 2007-12-21 10:29 ` Andrew Morton 2007-12-21 11:34 ` Eric Dumazet
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