From: John Ogness <john.ogness@linutronix.de>
To: Petr Mladek <pmladek@suse.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>,
Kieran Bingham <kbingham@kernel.org>,
linux-kernel@vger.kernel.org
Subject: [PATCH] scripts/gdb: lx-dmesg: read records individually
Date: Wed, 15 Dec 2021 16:16:22 +0106 [thread overview]
Message-ID: <874k79c3a9.fsf@jogness.linutronix.de> (raw)
For the gdb command lx-dmesg, the entire descriptor, info, and text
data regions are read into memory before printing any records. For
large kernel log buffers, this not only causes a huge delay before
seeing any records, but it may also lead to python errors of too
much memory allocation.
Rather than reading in all these regions in advance, read them as
needed and only read the regions for the particular record that is
being printed.
The gdb macro "dmesg" in Documentation/admin-guide/kdump/gdbmacros.txt
already prints out the kernel log buffer like this.
Signed-off-by: John Ogness <john.ogness@linutronix.de>
---
scripts/gdb/linux/dmesg.py | 35 ++++++++++++++++++-----------------
1 file changed, 18 insertions(+), 17 deletions(-)
diff --git a/scripts/gdb/linux/dmesg.py b/scripts/gdb/linux/dmesg.py
index a92c55bd8de5..d5983cf3db7d 100644
--- a/scripts/gdb/linux/dmesg.py
+++ b/scripts/gdb/linux/dmesg.py
@@ -44,19 +44,17 @@ class LxDmesg(gdb.Command):
sz = prb_desc_ring_type.get_type().sizeof
desc_ring = utils.read_memoryview(inf, addr, sz).tobytes()
- # read in descriptor array
+ # read in descriptor count, size, and address
off = prb_desc_ring_type.get_type()['count_bits'].bitpos // 8
desc_ring_count = 1 << utils.read_u32(desc_ring, off)
desc_sz = prb_desc_type.get_type().sizeof
off = prb_desc_ring_type.get_type()['descs'].bitpos // 8
- addr = utils.read_ulong(desc_ring, off)
- descs = utils.read_memoryview(inf, addr, desc_sz * desc_ring_count).tobytes()
+ desc_addr = utils.read_ulong(desc_ring, off)
- # read in info array
+ # read in info size and address
info_sz = printk_info_type.get_type().sizeof
off = prb_desc_ring_type.get_type()['infos'].bitpos // 8
- addr = utils.read_ulong(desc_ring, off)
- infos = utils.read_memoryview(inf, addr, info_sz * desc_ring_count).tobytes()
+ info_addr = utils.read_ulong(desc_ring, off)
# read in text data ring structure
off = printk_ringbuffer_type.get_type()['text_data_ring'].bitpos // 8
@@ -64,12 +62,11 @@ class LxDmesg(gdb.Command):
sz = prb_data_ring_type.get_type().sizeof
text_data_ring = utils.read_memoryview(inf, addr, sz).tobytes()
- # read in text data
+ # read in text data size and address
off = prb_data_ring_type.get_type()['size_bits'].bitpos // 8
text_data_sz = 1 << utils.read_u32(text_data_ring, off)
off = prb_data_ring_type.get_type()['data'].bitpos // 8
- addr = utils.read_ulong(text_data_ring, off)
- text_data = utils.read_memoryview(inf, addr, text_data_sz).tobytes()
+ text_data_addr = utils.read_ulong(text_data_ring, off)
counter_off = atomic_long_type.get_type()['counter'].bitpos // 8
@@ -102,17 +99,20 @@ class LxDmesg(gdb.Command):
desc_off = desc_sz * ind
info_off = info_sz * ind
+ desc = utils.read_memoryview(inf, desc_addr + desc_off, desc_sz).tobytes()
+
# skip non-committed record
- state = 3 & (utils.read_u64(descs, desc_off + sv_off +
- counter_off) >> desc_flags_shift)
+ state = 3 & (utils.read_u64(desc, sv_off + counter_off) >> desc_flags_shift)
if state != desc_committed and state != desc_finalized:
if did == head_id:
break
did = (did + 1) & desc_id_mask
continue
- begin = utils.read_ulong(descs, desc_off + begin_off) % text_data_sz
- end = utils.read_ulong(descs, desc_off + next_off) % text_data_sz
+ begin = utils.read_ulong(desc, begin_off) % text_data_sz
+ end = utils.read_ulong(desc, next_off) % text_data_sz
+
+ info = utils.read_memoryview(inf, info_addr + info_off, info_sz).tobytes()
# handle data-less record
if begin & 1 == 1:
@@ -125,16 +125,17 @@ class LxDmesg(gdb.Command):
# skip over descriptor id
text_start = begin + utils.get_long_type().sizeof
- text_len = utils.read_u16(infos, info_off + len_off)
+ text_len = utils.read_u16(info, len_off)
# handle truncated message
if end - text_start < text_len:
text_len = end - text_start
- text = text_data[text_start:text_start + text_len].decode(
- encoding='utf8', errors='replace')
+ text_data = utils.read_memoryview(inf, text_data_addr + text_start,
+ text_len).tobytes()
+ text = text_data[0:text_len].decode(encoding='utf8', errors='replace')
- time_stamp = utils.read_u64(infos, info_off + ts_off)
+ time_stamp = utils.read_u64(info, ts_off)
for line in text.splitlines():
msg = u"[{time:12.6f}] {line}\n".format(
base-commit: 0bafb8f3ebc84525d0ae0fcea22d12151b99312f
--
2.30.2
next reply other threads:[~2021-12-15 15:10 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-15 15:10 John Ogness [this message]
2021-12-16 14:56 ` [PATCH] scripts/gdb: lx-dmesg: read records individually Petr Mladek
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=874k79c3a9.fsf@jogness.linutronix.de \
--to=john.ogness@linutronix.de \
--cc=jan.kiszka@siemens.com \
--cc=kbingham@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=pmladek@suse.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.