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Groups > linux.kernel > #1204181
| From | Wei Liu <wei.liu2@citrix.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v3 18/20] net/xen-netback: Make it running on 64KB page granularity |
| Date | 2015-08-10 13:40 +0200 |
| Message-ID | <pVTAR-53A-5@gated-at.bofh.it> (permalink) |
| References | <pUT0e-5e5-15@gated-at.bofh.it> <pUTtg-61C-21@gated-at.bofh.it> <pVdLk-1Rl-5@gated-at.bofh.it> <pVS28-2wD-49@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Mon, Aug 10, 2015 at 10:57:48AM +0100, Julien Grall wrote:
[...]
>
> >>+ info.page = page;
> >>+ gnttab_foreach_grant_in_range(page, offset, bytes,
> >>+ xenvif_gop_frag_copy_grant,
> >>+ &info);
> >
> >Looks like I need to at least wait until the API is settle before giving
> >my ack.
> >
> >> size -= bytes;
> >>+ offset = 0;
> >
> >This looks wrong. Should be offset += bytes.
>
> With the new implementation of the loop, each iteration will be on a
> different page.
> So only the first page has an offset different than zero.
>
> >
> >>
> >>- /* Next frame */
> >>- if (offset == PAGE_SIZE && size) {
> >>+ /* Next page */
> >>+ if (size) {
> >> BUG_ON(!PageCompound(page));
> >> page++;
> >>- offset = 0;
> >
> >And this should not be deleted, I think.
> >
> >What is the reason for changing offset calculation? I think there is
> >still compound page when using 64K page.
>
> The compound pages are still working ... gnttab_foreach_grant_in_range is
> called once per page. So the offset can be reset to 0 every time. No need to
> add code which would make the result less clear.
>
> We only need to know if the size is not 0 to get the next page.
>
> The patch may not be clear enough to see it's working so I've copied the
> result loop below:
>
> while (size > 0) {
> BUG_ON(offset >= PAGE_SIZE);
>
> bytes = PAGE_SIZE - offset;
> if (bytes > size)
> bytes = size;
>
> info.page = page;
> gnttab_foreach_grant_in_range(page, offset, bytes,
> xenvif_gop_frag_copy_grant,
> &info);
> size -= bytes;
> offset = 0;
>
> /* Next page */
> if (size) {
> BUG_ON(!PageCompound(page));
> page++;
> }
> }
>
Right. That doesn't mean the original code was wrong or anything. But I
don't want to bikeshed about this.
Please add a comment saying that offset is always 0 starting from second
iteration because the gnttab_foreach_grant_in_range makes sure we handle
one page in one go.
Wei.
> Regards,
>
> --
> Julien Grall
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[PATCH v3 00/20] xen/arm64: Add support for 64KB page Julien Grall <julien.grall@citrix.com> - 2015-08-07 18:50 +0200
[PATCH v3 09/20] xen/biomerge: Don't allow biovec to be merge when Linux is not using 4KB page Julien Grall <julien.grall@citrix.com> - 2015-08-07 18:50 +0200
Re: [PATCH v3 09/20] xen/biomerge: Don't allow biovec to be merge when Linux is not using 4KB page Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-08-10 13:00 +0200
Re: [Xen-devel] [PATCH v3 09/20] xen/biomerge: Don't allow biovec to be merge when Linux is not using 4KB page Julien Grall <julien.grall@citrix.com> - 2015-08-10 13:30 +0200
Re: [Xen-devel] [PATCH v3 09/20] xen/biomerge: Don't allow biovec to be merge when Linux is not using 4KB page Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-08-10 13:30 +0200
Re: [Xen-devel] [PATCH v3 09/20] xen/biomerge: Don't allow biovec to be merge when Linux is not using 4KB page Julien Grall <julien.grall@citrix.com> - 2015-08-10 13:40 +0200
Re: [Xen-devel] [PATCH v3 09/20] xen/biomerge: Don't allow biovec to be merge when Linux is not using 4KB page David Vrabel <david.vrabel@citrix.com> - 2015-08-10 14:50 +0200
[PATCH v3 07/20] block/xen-blkfront: Store a page rather a pfn in the grant structure Julien Grall <julien.grall@citrix.com> - 2015-08-07 18:50 +0200
[PATCH v3 06/20] block/xen-blkfront: Split blkif_queue_request in 2 Julien Grall <julien.grall@citrix.com> - 2015-08-07 18:50 +0200
[PATCH v3 03/20] xen: Add Xen specific page definition Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:00 +0200
Re: [PATCH v3 03/20] xen: Add Xen specific page definition Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-08-10 12:50 +0200
[PATCH v3 01/20] net/xen-netback: xenvif_gop_frag_copy: move GSO check out of the loop Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:00 +0200
Re: [PATCH v3 01/20] net/xen-netback: xenvif_gop_frag_copy: move GSO check out of the loop Wei Liu <wei.liu2@citrix.com> - 2015-08-08 16:00 +0200
[PATCH v3 14/20] xen/grant-table: Make it running on 64KB granularity Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:20 +0200
Re: [Xen-devel] [PATCH v3 00/20] xen/arm64: Add support for 64KB page Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:20 +0200
[PATCH v3 10/20] xen/xenbus: Use Xen page definition Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:20 +0200
[PATCH v3 17/20] net/xen-netfront: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:20 +0200
[PATCH v3 11/20] tty/hvc: xen: Use xen page definition Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:20 +0200
[PATCH v3 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:20 +0200
Re: [PATCH v3 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-08-10 13:20 +0200
Re: [PATCH v3 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux Julien Grall <julien.grall@citrix.com> - 2015-08-10 13:40 +0200
Re: [PATCH v3 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-08-10 15:00 +0200
Re: [PATCH v3 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux Julien Grall <julien.grall@citrix.com> - 2015-08-10 15:40 +0200
[PATCH v3 13/20] xen/events: fifo: Make it running on 64KB granularity Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:20 +0200
[PATCH v3 19/20] xen/privcmd: Add support for Linux 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:20 +0200
Re: [PATCH v3 19/20] xen/privcmd: Add support for Linux 64KB page granularity Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-08-10 14:10 +0200
Re: [Xen-devel] [PATCH v3 19/20] xen/privcmd: Add support for Linux 64KB page granularity David Vrabel <david.vrabel@citrix.com> - 2015-08-10 14:20 +0200
Re: [Xen-devel] [PATCH v3 19/20] xen/privcmd: Add support for Linux 64KB page granularity Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-08-10 15:00 +0200
Re: [Xen-devel] [PATCH v3 19/20] xen/privcmd: Add support for Linux 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-08-10 15:30 +0200
[PATCH v3 18/20] net/xen-netback: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:20 +0200
Re: [PATCH v3 18/20] net/xen-netback: Make it running on 64KB page granularity Wei Liu <wei.liu2@citrix.com> - 2015-08-08 17:00 +0200
Re: [PATCH v3 18/20] net/xen-netback: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-08-10 12:00 +0200
Re: [PATCH v3 18/20] net/xen-netback: Make it running on 64KB page granularity Wei Liu <wei.liu2@citrix.com> - 2015-08-10 13:40 +0200
Re: [PATCH v3 18/20] net/xen-netback: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-08-10 14:10 +0200
[PATCH v3 15/20] block/xen-blkfront: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:20 +0200
[PATCH v3 16/20] block/xen-blkback: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:20 +0200
[PATCH v3 20/20] arm/xen: Add support for 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:20 +0200
Re: [PATCH v3 20/20] arm/xen: Add support for 64KB page granularity Stefano Stabellini <stefano.stabellini@eu.citrix.com> - 2015-08-10 15:00 +0200
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