linux-toradex.git/Documentation, branch v3.2.23

stable: Allow merging of backports for serious user-visible performance issues

2012-07-04T04:44:29+00:00

commit eb3979f64d25120d60b9e761a4c58f70b1a02f86 upstream.

Distribution kernel maintainers routinely backport fixes for users that
were deemed important but not "something critical" as defined by the
rules. To users of these kernels they are very serious and failing to fix
them reduces the value of -stable.

The problem is that the patches fixing these issues are often subtle and
prone to regressions in other ways and need greater care and attention.
To combat this, these "serious" backports should have a higher barrier
to entry.

This patch relaxes the rules to allow a distribution maintainer to merge
to -stable a backported patch or small series that fixes a "serious"
user-visible performance issue. They should include additional information on
the user-visible bug affected and a link to the bugzilla entry if available.
The same rules about the patch being already in mainline still apply.

Signed-off-by: Mel Gorman 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Ben Hutchings

docs: update HOWTO for 2.6.x -> 3.x versioning

2012-05-30T23:43:30+00:00

commit 591bfc6bf9e5e25e464fd4c87d64afd5135667c4 upstream.

The HOWTO document needed updating for the new kernel versioning. The
git URI for -next was updated as well.

Signed-off-by: Kees Cook 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Ben Hutchings

tcp: change tcp_adv_win_scale and tcp_rmem[2]

2012-05-20T21:56:38+00:00

[ Upstream commit b49960a05e32121d29316cfdf653894b88ac9190 ]

tcp_adv_win_scale default value is 2, meaning we expect a good citizen
skb to have skb->len / skb->truesize ratio of 75% (3/4)

In 2.6 kernels we (mis)accounted for typical MSS=1460 frame :
1536 + 64 + 256 = 1856 'estimated truesize', and 1856 * 3/4 = 1392.
So these skbs were considered as not bloated.

With recent truesize fixes, a typical MSS=1460 frame truesize is now the
more precise :
2048 + 256 = 2304. But 2304 * 3/4 = 1728.
So these skb are not good citizen anymore, because 1460 < 1728

(GRO can escape this problem because it build skbs with a too low
truesize.)

This also means tcp advertises a too optimistic window for a given
allocated rcvspace : When receiving frames, sk_rmem_alloc can hit
sk_rcvbuf limit and we call tcp_prune_queue()/tcp_collapse() too often,
especially when application is slow to drain its receive queue or in
case of losses (netperf is fast, scp is slow). This is a major latency
source.

We should adjust the len/truesize ratio to 50% instead of 75%

This patch :

1) changes tcp_adv_win_scale default to 1 instead of 2

2) increase tcp_rmem[2] limit from 4MB to 6MB to take into account
better truesize tracking and to allow autotuning tcp receive window to
reach same value than before. Note that same amount of kernel memory is
consumed compared to 2.6 kernels.

Signed-off-by: Eric Dumazet 
Cc: Neal Cardwell 
Cc: Tom Herbert 
Cc: Yuchung Cheng 
Acked-by: Neal Cardwell 
Signed-off-by: David S. Miller 
Signed-off-by: Ben Hutchings

hwmon: (zl6100) Enable interval between chip accesses for all chips

2012-03-19T16:02:36+00:00

commit fecfb64422d91a9621a3f96ab75c3a5f13e80b58 upstream.

Intersil reports that all chips supported by the zl6100 driver require
an interval between chip accesses, even ZL2004 and ZL6105 which were thought
to be safe.

Reported-by: Vivek Gani 
Signed-off-by: Guenter Roeck 
Signed-off-by: Greg Kroah-Hartman

hwmon: (w83627ehf) Fix temp2 source for W83627UHG

2012-03-19T16:02:35+00:00

commit aacb6b0052692c72fe0cb94c6b547202def6ef46 upstream.

Properly set the source of temp2 for the W83627UHG. Also fix a
comment right before that, and document the W83627UHG as reporting up
to 3 temperatures.

Signed-off-by: Jean Delvare 
Cc: Guenter Roeck 
Signed-off-by: Guenter Roeck 
Signed-off-by: Greg Kroah-Hartman

hwmon: (jc42) Add support for AT30TS00, TS3000GB2, TSE2002GB2, and MCP9804

2012-03-12T19:31:40+00:00

commit 1bd612a25855f4cc9345052b53d7da697dba6358 upstream.

Also update IDT datasheet locations.

Signed-off-by: Guenter Roeck 
Acked-by: Jean Delvare 
Signed-off-by: Greg Kroah-Hartman

hwmon: (jc42) Add support for ST Microelectronics STTS2002 and STTS3000

2012-03-12T19:31:40+00:00

commit 4de86126a712ba83fa038d277c8282f7ed466a4b upstream.

These are fully compatible with Jedec JC 42.4 as far as I can see.

Signed-off-by: Jean Delvare 
Cc: Guenter Roeck 
Signed-off-by: Guenter Roeck 
Signed-off-by: Greg Kroah-Hartman

USB: update documentation for usbmon

2012-01-12T19:29:34+00:00

commit d8cae98cddd286e38db1724dda1b0e7b467f9237 upstream.

The documentation for usbmon is out of date; the usbfs "devices" file
now exists in /sys/kernel/debug/usb rather than /proc/bus/usb.  This
patch (as1505) updates the documentation accordingly, and also
mentions that the necessary information can be found by running lsusb.

Signed-off-by: Alan Stern 
CC: Pete Zaitcev 
Signed-off-by: Greg Kroah-Hartman

Documentation: Update stable address

2012-01-12T19:29:17+00:00

commit 2eb7f204db51969ea558802a6601d79c2fb273b9 upstream.

The Japanese/Korean/Chinese versions still need updating.

Also, the stable kernel 2.6.x.y descriptions are out of date
and should be updated as well.

Signed-off-by: Joe Perches 
Signed-off-by: Greg Kroah-Hartman

KVM: Don't automatically expose the TSC deadline timer in cpuid

2011-12-26T11:27:44+00:00

Unlike all of the other cpuid bits, the TSC deadline timer bit is set
unconditionally, regardless of what userspace wants.

This is broken in several ways:
 - if userspace doesn't use KVM_CREATE_IRQCHIP, and doesn't emulate the TSC
   deadline timer feature, a guest that uses the feature will break
 - live migration to older host kernels that don't support the TSC deadline
   timer will cause the feature to be pulled from under the guest's feet;
   breaking it
 - guests that are broken wrt the feature will fail.

Fix by not enabling the feature automatically; instead report it to userspace.
Because the feature depends on KVM_CREATE_IRQCHIP, which we cannot guarantee
will be called, we expose it via a KVM_CAP_TSC_DEADLINE_TIMER and not
KVM_GET_SUPPORTED_CPUID.

Fixes the Illumos guest kernel, which uses the TSC deadline timer feature.

[avi: add the KVM_CAP + documentation]

Reported-by: Alexey Zaytsev 
Tested-by: Alexey Zaytsev 
Signed-off-by: Jan Kiszka 
Signed-off-by: Avi Kivity