On Mon, Feb 20, 2017 at 6:15 PM, J. Bruce Fields <bfields@xxxxxxxxxx> wrote: > On Mon, Feb 20, 2017 at 11:42:31AM -0500, Chuck Lever wrote: >> >> > On Feb 20, 2017, at 11:09 AM, J. Bruce Fields <bfields@xxxxxxxxxx> wrote: >> > >> > On Sun, Feb 19, 2017 at 02:29:03PM -0500, Chuck Lever wrote: >> >> >> >>> On Feb 18, 2017, at 9:07 PM, J. Bruce Fields <bfields@xxxxxxxxxx> wrote: >> >>> >> >>> From: Weston Andros Adamson <dros@xxxxxxxxxx> >> >>> >> >>> Instead of preallocating pags, allow xdr_partial_copy_from_skb() to >> >>> allocate whatever pages we need on demand. This is what the NFSv3 ACL >> >>> code does. >> >> >> >> The patch description does not explain why this change is >> >> being done. >> > >> > The only justification I see is avoiding allocating pages unnecessarily. >> >> That makes sense. Is there a real world workload that has seen >> a negative effect? >> >> >> > Without this patch, for each getacl, we allocate 17 pages (if I'm >> > calculating correctly) and probably rarely use most of them. >> > >> > In the v3 case I think it's 7 pages instead of 17. >> >> I would have guessed 9. Out of curiosity, is there a reason >> documented for these size limits? > > > In the v4 case: > > #define NFS4ACL_MAXPAGES DIV_ROUND_UP(XATTR_SIZE_MAX, PAGE_SIZE) > > And I believe XATTR_SIZE_MAX is a global maximum on the size of any > extend attribute value. XATTR_SIZE_MAX is the maximum size of an extended attribute. NFSv4 ACLs are passed through unchanged in "system.nfs4_acl". > In the v3 case: > > /* Maximum number of ACL entries over NFS */ > #define NFS_ACL_MAX_ENTRIES 1024 > > #define NFSACL_MAXPAGES ((2*(8+12*NFS_ACL_MAX_ENTRIES) + PAGE_SIZE-1) \ > >> PAGE_SHIFT) > > No idea where that 1024 comes from. The 1024-entry limit is arbitrary. Andreas -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
