Messages in this thread Patch in this message | | | Date | Sat, 31 May 2008 10:50:40 +0100 | From | Jeremy Fitzhardinge <> | Subject | Re: [PATCH 5 of 5] xen: Avoid allocations causing swap activity on the resume path |
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Jeff Garzik wrote: > Jeremy Fitzhardinge wrote: >> From: Ian Campbell <ian.campbell@citrix.com> >> >> Avoid allocations causing swap activity on the resume path by allowing >> such allocations to access the emergency pools otherwise a >> save/restore/migration of a guest which is low on memory can >> deadlock. >> >> [ linux-2.6.18-xen changesets e8b49cfbdac, fdb998e79aba ] >> >> Signed-off-by: Ian Campbell <ian.campbell@citrix.com> >> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> >> >> --- >> drivers/block/xen-blkfront.c | 5 +++-- >> drivers/net/xen-netfront.c | 4 ++-- >> drivers/xen/xenbus/xenbus_client.c | 2 +- >> drivers/xen/xenbus/xenbus_xs.c | 10 +++++----- >> 4 files changed, 11 insertions(+), 10 deletions(-) > > IMO I am not qualified enough to ACK or NAK this VM-related patch...
Yeah, I'm not quite sure about which GFP_ flags to use in what circumstance. In this case the potential for deadlock exists because this is the code which is reconnecting the virtual devices after a resume, which will probably include its storage (either block device, or some kind of network storage). Should GFP_NOFS also be in there? Something else? Does __GFP_HIGH necessarily mean that it won't try to do IO to push pages out?
Thanks, J
Patch again for reference:
Subject: xen: Avoid allocations causing swap activity on the resume path
From: Ian Campbell <ian.campbell@citrix.com>
Avoid allocations causing swap activity on the resume path by allowing such allocations to access the emergency pools otherwise a save/restore/migration of a guest which is low on memory can deadlock.
[ linux-2.6.18-xen changesets e8b49cfbdac, fdb998e79aba ]
Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
--- drivers/block/xen-blkfront.c | 5 +++-- drivers/net/xen-netfront.c | 4 ++-- drivers/xen/xenbus/xenbus_client.c | 2 +- drivers/xen/xenbus/xenbus_xs.c | 10 +++++----- 4 files changed, 11 insertions(+), 10 deletions(-)
=================================================================== --- a/drivers/block/xen-blkfront.c +++ b/drivers/block/xen-blkfront.c @@ -584,7 +584,7 @@ info->ring_ref = GRANT_INVALID_REF; - sring = (struct blkif_sring *)__get_free_page(GFP_KERNEL); + sring = (struct blkif_sring *)__get_free_page(GFP_KERNEL | __GFP_HIGH); if (!sring) { xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring"); return -ENOMEM; @@ -741,7 +741,8 @@ int j; /* Stage 1: Make a safe copy of the shadow state. */ - copy = kmalloc(sizeof(info->shadow), GFP_KERNEL); + copy = kmalloc(sizeof(info->shadow), + GFP_KERNEL | __GFP_NOFAIL | __GFP_HIGH); if (!copy) return -ENOMEM; memcpy(copy, info->shadow, sizeof(info->shadow)); =================================================================== --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -1324,7 +1324,7 @@ goto fail; } - txs = (struct xen_netif_tx_sring *)get_zeroed_page(GFP_KERNEL); + txs = (struct xen_netif_tx_sring *)get_zeroed_page(GFP_KERNEL | __GFP_HIGH); if (!txs) { err = -ENOMEM; xenbus_dev_fatal(dev, err, "allocating tx ring page"); @@ -1340,7 +1340,7 @@ } info->tx_ring_ref = err; - rxs = (struct xen_netif_rx_sring *)get_zeroed_page(GFP_KERNEL); + rxs = (struct xen_netif_rx_sring *)get_zeroed_page(GFP_KERNEL | __GFP_HIGH); if (!rxs) { err = -ENOMEM; xenbus_dev_fatal(dev, err, "allocating rx ring page"); =================================================================== --- a/drivers/xen/xenbus/xenbus_client.c +++ b/drivers/xen/xenbus/xenbus_client.c @@ -117,7 +117,7 @@ char *path; va_start(ap, pathfmt); - path = kvasprintf(GFP_KERNEL, pathfmt, ap); + path = kvasprintf(GFP_KERNEL | __GFP_HIGH, pathfmt, ap); va_end(ap); if (!path) { =================================================================== --- a/drivers/xen/xenbus/xenbus_xs.c +++ b/drivers/xen/xenbus/xenbus_xs.c @@ -283,9 +283,9 @@ char *buffer; if (strlen(name) == 0) - buffer = kasprintf(GFP_KERNEL, "%s", dir); + buffer = kasprintf(GFP_KERNEL | __GFP_HIGH, "%s", dir); else - buffer = kasprintf(GFP_KERNEL, "%s/%s", dir, name); + buffer = kasprintf(GFP_KERNEL | __GFP_HIGH, "%s/%s", dir, name); return (!buffer) ? ERR_PTR(-ENOMEM) : buffer; } @@ -297,7 +297,7 @@ *num = count_strings(strings, len); /* Transfer to one big alloc for easy freeing. */ - ret = kmalloc(*num * sizeof(char *) + len, GFP_KERNEL); + ret = kmalloc(*num * sizeof(char *) + len, GFP_KERNEL | __GFP_HIGH); if (!ret) { kfree(strings); return ERR_PTR(-ENOMEM); @@ -751,7 +751,7 @@ } - msg = kmalloc(sizeof(*msg), GFP_KERNEL); + msg = kmalloc(sizeof(*msg), GFP_KERNEL | __GFP_HIGH); if (msg == NULL) { err = -ENOMEM; goto out; @@ -763,7 +763,7 @@ goto out; } - body = kmalloc(msg->hdr.len + 1, GFP_KERNEL); + body = kmalloc(msg->hdr.len + 1, GFP_KERNEL | __GFP_HIGH); if (body == NULL) { kfree(msg); err = -ENOMEM;
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