Hi Andreas- > On Feb 20, 2017, at 4:31 PM, Andreas Gruenbacher <agruenba@xxxxxxxxxx> wrote: > > 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". "Extended attribute" means this is a Linux-specific limit? Is there anything that prevents a non-Linux system from constructing or returning an ACL that is larger than that? What happens on a Linux client when a server returns an ACL that does not fit in this allotment? >> 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 -- Chuck Lever -- 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
