On 06/19/17 at 03:23pm, Cong Wang wrote: > In kdump kernel, we got: > > Saving vmcore-dmesg.txt > Failed to malloc 67108864 bytes for the logbuf: Cannot allocate memory > > Apparently 64M is too luxury for a kdump kernel which only has 128M > in total. > > We can avoid allocating such a large memory chunk, instead just allocate > a smaller chunk inside the loop each time. > > Verify the result by comparing the vmcore-dmesg output with and without > this patch. > > Cc: Simon Horman <[email protected]> > Signed-off-by: Cong Wang <[email protected]> > --- > vmcore-dmesg/vmcore-dmesg.c | 101 > ++++++++++++++++++-------------------------- > 1 file changed, 41 insertions(+), 60 deletions(-) > > diff --git a/vmcore-dmesg/vmcore-dmesg.c b/vmcore-dmesg/vmcore-dmesg.c > index a8f56df..593557c 100644 > --- a/vmcore-dmesg/vmcore-dmesg.c > +++ b/vmcore-dmesg/vmcore-dmesg.c > @@ -565,53 +565,12 @@ static inline uint64_t struct_val_u64(char *ptr, > unsigned int offset) > return(file64_to_cpu(*(uint64_t *)(ptr + offset))); > } > > -/* human readable text of the record */ > -static char *log_text(char *msg) > -{ > - return msg + log_sz; > -} > - > -/* get record by index; idx must point to valid msg */ > -static char *log_from_idx(char *log_buf, uint32_t idx) > -{ > - char *msg = log_buf + idx; > - > - /* > - * A length == 0 record is the end of buffer marker. Wrap around and > - * read the message at the start of the buffer. > - */ > - if (!struct_val_u16(msg, log_offset_len)) > - return log_buf; > - return msg; > -} > - > -/* get next record; idx must point to valid msg */ > -static uint32_t log_next(char *log_buf, uint32_t idx) > -{ > - char *msg = log_buf + idx; > - uint16_t len; > - > - /* length == 0 indicates the end of the buffer; wrap */ > - /* > - * A length == 0 record is the end of buffer marker. Wrap around and > - * read the message at the start of the buffer as *this* one, and > - * return the one after that. > - */ > - len = struct_val_u16(msg, log_offset_len); > - if (!len) { > - msg = log_buf; > - return struct_val_u16(msg, log_offset_len); > - } > - return idx + len; > -} > - > /* Read headers of log records and dump accordingly */ > static void dump_dmesg_structured(int fd) > { > #define OUT_BUF_SIZE 4096 > uint64_t log_buf, log_buf_offset, ts_nsec; > uint32_t log_first_idx, log_next_idx, current_idx, len = 0, i; > - int log_buf_len; > char *buf, out_buf[OUT_BUF_SIZE]; > ssize_t ret; > char *msg; > @@ -659,34 +618,33 @@ static void dump_dmesg_structured(int fd) > } > > log_buf = read_file_pointer(fd, vaddr_to_offset(log_buf_vaddr)); > - log_buf_len = read_file_s32(fd, vaddr_to_offset(log_buf_len_vaddr)); > > log_first_idx = read_file_u32(fd, vaddr_to_offset(log_first_idx_vaddr)); > log_next_idx = read_file_u32(fd, vaddr_to_offset(log_next_idx_vaddr)); > > log_buf_offset = vaddr_to_offset(log_buf); > > - buf = calloc(1, log_buf_len); > + buf = calloc(1, log_sz); > if (!buf) { > - fprintf(stderr, "Failed to malloc %d bytes for the logbuf:" > - " %s\n", log_buf_len, strerror(errno)); > + fprintf(stderr, "Failed to malloc %" PRId64 " bytes for the > log:" > + " %s\n", log_sz, strerror(errno)); > exit(64); > } > > - ret = pread(fd, buf, log_buf_len, log_buf_offset); > - if (ret != log_buf_len) { > - fprintf(stderr, "Failed to read log buffer of size %d bytes:" > - " %s\n", log_buf_len, strerror(errno)); > - exit(65); > - } > - > /* Parse records and write out data at standard output */ > > current_idx = log_first_idx; > len = 0; > while (current_idx != log_next_idx) { > - msg = log_from_idx(buf, current_idx); > - ts_nsec = struct_val_u64(msg, log_offset_ts_nsec); > + uint16_t loglen; > + > + ret = pread(fd, buf, log_sz, log_buf_offset + current_idx); > + if (ret != log_sz) { > + fprintf(stderr, "Failed to read log of size %" PRId64 " > bytes:" > + " %s\n", log_sz, strerror(errno)); > + exit(65); > + } > + ts_nsec = struct_val_u64(buf, log_offset_ts_nsec); > imaxdiv_sec = imaxdiv(ts_nsec, 1000000000); > imaxdiv_usec = imaxdiv(imaxdiv_sec.rem, 1000); > > @@ -695,9 +653,22 @@ static void dump_dmesg_structured(int fd) > (long long unsigned int)imaxdiv_usec.quot); > > /* escape non-printable characters */ > - text_len = struct_val_u16(msg, log_offset_text_len); > + text_len = struct_val_u16(buf, log_offset_text_len); > + msg = calloc(1, text_len); > + if (!msg) { > + fprintf(stderr, "Failed to malloc %u bytes for log > text:" > + " %s\n", text_len, strerror(errno)); > + exit(64); > + } > + > + ret = pread(fd, msg, text_len, log_buf_offset + current_idx + > log_sz); > + if (ret != text_len) { > + fprintf(stderr, "Failed to read log text of size %u > bytes:" > + " %s\n", text_len, strerror(errno)); > + exit(65); > + } > for (i = 0; i < text_len; i++) { > - unsigned char c = log_text(msg)[i]; > + unsigned char c = msg[i]; > > if (!isprint(c) && !isspace(c)) > len += sprintf(out_buf + len, "\\x%02x", c); > @@ -711,11 +682,21 @@ static void dump_dmesg_structured(int fd) > } > > out_buf[len++] = '\n'; > - > - /* Move to next record */ > - current_idx = log_next(buf, current_idx); > + free(msg); > + /* length == 0 indicates the end of the buffer; wrap */
Since the code is restructured, above line can be dropped, other wise: Reviewed-by: Dave Young <[email protected]> > + /* > + * A length == 0 record is the end of buffer marker. Wrap > around and > + * read the message at the start of the buffer as *this* one, > and > + * return the one after that. > + */ > + loglen = struct_val_u16(buf, log_offset_len); > + if (!loglen) > + current_idx = log_first_idx; > + else > + /* Move to next record */ > + current_idx += loglen; > } > - > + free(buf); > if (len) > write_to_stdout(out_buf, len); > } > -- > 2.5.5 > > > _______________________________________________ > kexec mailing list > [email protected] > http://lists.infradead.org/mailman/listinfo/kexec Thanks Dave > > _______________________________________________ kexec mailing list [email protected] http://lists.infradead.org/mailman/listinfo/kexec
