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Groups > linux.kernel > #1210274
| From | Roger Pau Monné <roger.pau@citrix.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v3 15/20] block/xen-blkfront: Make it running on 64KB page granularity |
| Date | 2015-08-20 10:20 +0200 |
| Message-ID | <pZteP-7Cz-37@gated-at.bofh.it> (permalink) |
| References | <pUT0e-5e5-15@gated-at.bofh.it> <pUTtg-61C-25@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
Hello,
I have some comments regarding the commit message, IMHO it would be good
that a native English speaker reviews it too.
El 07/08/15 a les 18.46, Julien Grall ha escrit:
> The PV block protocol is using 4KB page granularity. The goal of this
> patch is to allow a Linux using 64KB page granularity using block
> device on a non-modified Xen.
>
> The block API is using segment which should at least be the size of a
> Linux page. Therefore, the driver will have to break the page in chunk
> of 4K before giving the page to the backend.
>
> Breaking a 64KB segment in 4KB chunk will result to have some chunk with
> no data.
I would rewrite the above line as:
When breaking a 64KB segment into 4KB chunks it is possible that some
chunks are empty.
> As the PV protocol always require to have data in the chunk, we
> have to count the number of Xen page which will be in use and avoid to
^pages
> sent empty chunk.
^and avoid sending empty chunks.
>
> Note that, a pre-defined number of grant is reserved before preparing
^grants are
> the request. This pre-defined number is based on the number and the
> maximum size of the segments. If each segment contain a very small
^contains
> amount of data, the driver may reserve too much grant (16 grant is
^many grants ^grants are
> reserved per segment with 64KB page granularity).
>
> Futhermore, in the case of persistent grant we allocate one Linux page
^grants
> per grant although only the 4KB of the page will be effectively use.
^first ^in
> This could be improved by share the page with multiple grants.
^sharing
>
> Signed-off-by: Julien Grall <julien.grall@citrix.com>
LGTM:
Acked-by: Roger Pau Monné <roger.pau@citrix.com>
Just one question.
[...]
> @@ -559,73 +669,30 @@ static int blkif_queue_rw_req(struct request *req)
> ring_req->operation = 0;
> }
> }
> - ring_req->u.rw.nr_segments = nseg;
> - }
> - for_each_sg(info->shadow[id].sg, sg, nseg, i) {
> - fsect = sg->offset >> 9;
> - lsect = fsect + (sg->length >> 9) - 1;
> -
> - if ((ring_req->operation == BLKIF_OP_INDIRECT) &&
> - (i % SEGS_PER_INDIRECT_FRAME == 0)) {
> - if (segments)
> - kunmap_atomic(segments);
> -
> - n = i / SEGS_PER_INDIRECT_FRAME;
> - gnt_list_entry = get_indirect_grant(&gref_head, info);
> - info->shadow[id].indirect_grants[n] = gnt_list_entry;
> - segments = kmap_atomic(gnt_list_entry->page);
> - ring_req->u.indirect.indirect_grefs[n] = gnt_list_entry->gref;
> - }
> -
> - gnt_list_entry = get_grant(&gref_head,
> - xen_page_to_gfn(sg_page(sg)),
> - info);
> - ref = gnt_list_entry->gref;
> -
> - info->shadow[id].grants_used[i] = gnt_list_entry;
> -
> - if (rq_data_dir(req) && info->feature_persistent) {
> - char *bvec_data;
> - void *shared_data;
> + ring_req->u.rw.nr_segments = num_grant;
> + }
>
> - BUG_ON(sg->offset + sg->length > PAGE_SIZE);
> + setup.ring_req = ring_req;
> + setup.id = id;
> + for_each_sg(info->shadow[id].sg, sg, num_sg, i) {
> + BUG_ON(sg->offset + sg->length > PAGE_SIZE);
>
> - shared_data = kmap_atomic(gnt_list_entry->page);
> - bvec_data = kmap_atomic(sg_page(sg));
> + if (setup.need_copy) {
> + setup.bvec_off = sg->offset;
> + setup.bvec_data = kmap_atomic(sg_page(sg));
> + }
>
> - /*
> - * this does not wipe data stored outside the
> - * range sg->offset..sg->offset+sg->length.
> - * Therefore, blkback *could* see data from
> - * previous requests. This is OK as long as
> - * persistent grants are shared with just one
> - * domain. It may need refactoring if this
> - * changes
> - */
> - memcpy(shared_data + sg->offset,
> - bvec_data + sg->offset,
> - sg->length);
> + gnttab_foreach_grant_in_range(sg_page(sg),
> + sg->offset,
> + sg->length,
> + blkif_setup_rw_req_grant,
> + &setup);
If I'm understanding this right, on x86 gnttab_foreach_grant_in_range is
only going to perform one iteration, since XEN_PAGE_SIZE == PAGE_SIZE.
Roger.
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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
Re: [Xen-devel] [PATCH v3 03/20] xen: Add Xen specific page definition David Vrabel <david.vrabel@citrix.com> - 2015-08-20 11:50 +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
Re: [Xen-devel] [PATCH v3 17/20] net/xen-netfront: Make it running on 64KB page granularity David Vrabel <david.vrabel@citrix.com> - 2015-08-20 12:10 +0200
[PATCH v3 11/20] tty/hvc: xen: Use xen page definition Julien Grall <julien.grall@citrix.com> - 2015-08-07 19:20 +0200
Re: [Xen-devel] [PATCH v3 11/20] tty/hvc: xen: Use xen page definition David Vrabel <david.vrabel@citrix.com> - 2015-08-20 12:00 +0200
Re: [Xen-devel] [PATCH v3 11/20] tty/hvc: xen: Use xen page definition Julien Grall <julien.grall@citrix.com> - 2015-08-28 17:10 +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
Re: [Xen-devel] [PATCH v3 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux David Vrabel <david.vrabel@citrix.com> - 2015-08-20 12:10 +0200
Re: [Xen-devel] [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> - 2015-08-28 17:20 +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
Re: [PATCH v3 19/20] xen/privcmd: Add support for Linux 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-09-01 19:20 +0200
Re: [Xen-devel] [PATCH v3 19/20] xen/privcmd: Add support for Linux 64KB page granularity David Vrabel <david.vrabel@citrix.com> - 2015-08-20 12:10 +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
Re: [PATCH v3 15/20] block/xen-blkfront: Make it running on 64KB page granularity Roger Pau Monné <roger.pau@citrix.com> - 2015-08-20 10:20 +0200
Re: [PATCH v3 15/20] block/xen-blkfront: Make it running on 64KB page granularity Julien Grall <julien.grall@citrix.com> - 2015-08-28 17:40 +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
Re: [PATCH v3 16/20] block/xen-blkback: Make it running on 64KB page granularity Roger Pau Monné <roger.pau@citrix.com> - 2015-08-20 10:20 +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
Re: [Xen-devel] [PATCH v3 00/20] xen/arm64: Add support for 64KB page Julien Grall <julien.grall@citrix.com> - 2015-08-20 02:50 +0200
Re: [Xen-devel] [PATCH v3 00/20] xen/arm64: Add support for 64KB page Roger Pau Monné <roger.pau@citrix.com> - 2015-08-20 10:20 +0200
Re: [Xen-devel] [PATCH v3 00/20] xen/arm64: Add support for 64KB page David Vrabel <david.vrabel@citrix.com> - 2015-08-20 12:20 +0200
Re: [Xen-devel] [PATCH v3 00/20] xen/arm64: Add support for 64KB page Julien Grall <julien.grall@citrix.com> - 2015-08-20 17:10 +0200
Re: [Xen-devel] [PATCH v3 00/20] xen/arm64: Add support for 64KB page David Vrabel <david.vrabel@citrix.com> - 2015-08-20 17:20 +0200
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