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Not doing this was found to cause problems with sequences of allocation
(multi-page), freeing, and then again allocation of the same page upon
boot when interrupts are still disabled (causing the owner field to be
non-zero, thus making the allocator attempt a TLB flush and, in its
processing, triggering an assertion).
Reported-by: Tomasz Wroblewski <tomasz.wroblewski@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Tested-by: Tomasz Wroblewski <tomasz.wroblewski@citrix.com>
Acked-by: Keir Fraser <keir@xen.org>
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Rather than bumping their sizes to slightly above (a multiple of)
PAGE_SIZE (in order to store tracking information), thus requiring
a non-order-0 allocation even when no more than a page is being
requested, return the result of alloc_xenheap_pages() directly, and use
the struct page_info field underlying PFN_ORDER() to store the actual
size (needed for freeing the memory).
This leverages the fact that sub-allocation of memory obtained from the
page allocator can only ever result in non-page-aligned memory chunks
(with the exception of zero size allocations with sufficiently high
alignment being requested, which is why zero-size allocations now get
special cased).
Use the new property to simplify allocation of the trap info array for
PV guests on x86.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>
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Because of c/s 24707:96987c324a4f, dump_irqs() can now be called in an
irq context when a bug condition is encountered. If this is the case,
ignore the call to xsm_show_irq_ssid() and the subsequent call to
xfree().
This prevents an assertion failure in xfree(), and should allow all the
debug information to be dumped, before failing with a BUG() because of
the underlying race condition we are attempting to reproduce.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Rather than using the non-obvious conditional around an xfree() that
would be passed NULL only in the inverse case (which could easily get
removed by a future change on the basis that calling xfree(NULL) is
benign), switch the order of checks in xfree() itself and only suppress
the call to XSM that could potentially call xmalloc().
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>
Committed-by: Jan Beulich <jbeulich@suse.com>
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Certain (boot time) allocations are relatively large (particularly when
building with high NR_CPUS), but can also happen to be pretty far away
from a power-of-two size. Utilize the page allocator's (other than
Linux'es) capability of allowing to return space from higher-order
allocations in smaller pieces to return the unused parts immediately.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>
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Rather than having to match a call to one of the xmalloc() flavors with
a subsequent memset(), introduce a zeroing variant of each of those
flavors.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Keir Fraser <keir@xen.org>
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This was happening for xmalloc request sizes between 3921 and 3951
bytes. The reason being that xmem_pool_alloc() may add extra padding
to the requested size, making the total block size greater than a
page.
Rather than add yet more smarts about TLSF to _xmalloc(), we just
dumbly attempt any request smaller than a page via xmem_pool_alloc()
first, then fall back on xmalloc_whole_pages() if this fails.
Based on bug diagnosis and initial patch by John Byrne <john.l.byrne@hp.com>
Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
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Tmem, when called from a tmem-capable (paravirtualized) guest, makes
use of otherwise unutilized ("fallow") memory to create and manage
pools of pages that can be accessed from the guest either as
"ephemeral" pages or as "persistent" pages. In either case, the pages
are not directly addressible by the guest, only copied to and fro via
the tmem interface. Ephemeral pages are a nice place for a guest to
put recently evicted clean pages that it might need again; these pages
can be reclaimed synchronously by Xen for other guests or other uses.
Persistent pages are a nice place for a guest to put "swap" pages to
avoid sending them to disk. These pages retain data as long as the
guest lives, but count against the guest memory allocation.
Tmem pages may optionally be compressed and, in certain cases, can be
shared between guests. Tmem also handles concurrency nicely and
provides limited QoS settings to combat malicious DoS attempts.
Save/restore and live migration support is not yet provided.
Tmem is primarily targeted for an x86 64-bit hypervisor. On a 32-bit
x86 hypervisor, it has limited functionality and testing due to
limitations of the xen heap. Nearly all of tmem is
architecture-independent; three routines remain to be ported to ia64
and it should work on that architecture too. It is also structured to
be portable to non-Xen environments.
Tmem defaults off (for now) and must be enabled with a "tmem" xen boot
option (and does nothing unless a tmem-capable guest is running). The
"tmem_compress" boot option enables compression which takes about 10x
more CPU but approximately doubles the number of pages that can be
stored.
Tmem can be controlled via several "xm" commands and many interesting
tmem statistics can be obtained. A README and internal specification
will follow, but lots of useful prose about tmem, as well as Linux
patches, can be found at http://oss.oracle.com/projects/tmem .
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
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Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
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Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
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This patch replaces the Xen xmalloc engine with tlsf, an allocation
engine that is both more space efficient and time-bounded, especially
for allocation sizes between PAGE_SIZE/2 and PAGE_SIZE.
The file xmalloc.c is deprecated but not yet deleted. A simple
changein common/Makefile will change back to the legacy xmalloc/xfree
if needed for testing.
Code adapted from Nitin Gupta's tlsf-kmod, rev 229, found here:
http://code.google.com/p/compcache/source/browse/trunk/sub-projects/allocat=
ors/tlsf-kmod
with description and performance details here:
http://code.google.com/p/compcache/wiki/TLSFAllocator
(new Xen code uses 4K=3DPAGE_SIZE for the region size)
For detailed info on tlsf, see:
http://rtportal.upv.es/rtmalloc/
Signed-off-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Keir Fraser <keir.fraser@citrix.com>
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