On Wed, May 23, 2012 at 03:20:11PM -0700, Andrew Morton wrote: > On Wed, 23 May 2012 13:28:21 +0000 > Nathan Zimmer <[email protected]> wrote: > > > > > When tmpfs has the memory policy interleaved it always starts allocating at > > each file at node 0. > > When there are many small files the lower nodes fill up disproportionately. > > My proposed solution is to start a file at a randomly chosen node. > > > > ... > > > > --- a/include/linux/shmem_fs.h > > +++ b/include/linux/shmem_fs.h > > @@ -17,6 +17,7 @@ struct shmem_inode_info { > > char *symlink; /* unswappable short symlink */ > > }; > > struct shared_policy policy; /* NUMA memory alloc policy */ > > + int node_offset; /* bias for interleaved nodes */ > > struct list_head swaplist; /* chain of maybes on swap */ > > struct list_head xattr_list; /* list of shmem_xattr */ > > struct inode vfs_inode; > > diff --git a/mm/shmem.c b/mm/shmem.c > > index f99ff3e..58ef512 100644 > > --- a/mm/shmem.c > > +++ b/mm/shmem.c > > @@ -819,7 +819,7 @@ static struct page *shmem_alloc_page(gfp_t gfp, > > > > /* Create a pseudo vma that just contains the policy */ > > pvma.vm_start = 0; > > - pvma.vm_pgoff = index; > > + pvma.vm_pgoff = index + info->node_offset; > > pvma.vm_ops = NULL; > > pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index); > > > > @@ -1153,6 +1153,7 @@ static struct inode *shmem_get_inode(struct > > super_block *sb, const struct inode > > inode->i_fop = &shmem_file_operations; > > mpol_shared_policy_init(&info->policy, > > shmem_get_sbmpol(sbinfo)); > > + info->node_offset = node_random(&node_online_map); > > break; > > case S_IFDIR: > > inc_nlink(inode); > > The patch seems a bit arbitrary and hacky. It would have helped if you > had fully described how it works, and why this implementation was > chosen. > The patch attempt to spread out the node usage by starting files at nodes other then 0. node_offset is set to a random node when the inode is allocated.
> - Why alter (actually, lie about!) the offset-into-file? Could we > have similarly perturbed the address arg to alloc_page_vma() to do > the spreading? > Using the address arg would be better. It also makes clear that we should still be using the index for looking up the memory policy. > - The patch is dependent upon MPOL_INTERLEAVE being in effect, isn't > it? How do we guarantee that it is in force here? > The node_offset is only used when MPOL_INTERLEAVE is in effect. However node_offset is set unconditionally. It would be quite easy to only generate the offset when the policy is set to interleave. > - We look up the policy via mpol_shared_policy_lookup() using the > unperturbed index. Why? Should we be using index+info->node_offset > there? > This concern should be obviated using the address arg instead of 'altering' the vm_pgoff. > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to [email protected]. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ > Don't email: <a href=mailto:"[email protected]";> [email protected] </a> -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
