初学者指南:Linux内核代码阅读心得

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资源摘要信息:"Linux_code_read.rar_linux" Linux作为一款开源的操作系统,其核心——Linux内核,是整个系统最为核心和重要的部分。Linux内核是由全世界的开发者共同编写的,它负责管理系统的硬件资源、进程调度、内存管理等底层操作。对于想要深入了解Linux操作系统原理和提升系统编程能力的开发者而言,阅读Linux内核源代码是一项必不可少的学习任务。 本资源包名为"Linux_code_read.rar_linux",是一个专为学习Linux内核代码而设计的压缩包文件。它的内容包括了一本《Linux内核代码阅读》的电子书(Linux_code_read.pdf),以及一个文本文件(www.pudn.com.txt),后者可能包含有关该电子书或相关资源的补充信息或链接地址。 《Linux内核代码阅读》这本电子书是为Linux初学者量身打造的入门级指南。该书不仅适合那些对Linux内核充满好奇心的学习者,也适合那些希望通过直接阅读源代码来提升自己编程和系统理解能力的专业人士。它详细地介绍了Linux内核的基本架构、关键组件以及内核中的各种算法和数据结构。通过阅读这些内容,读者能够逐步建立起对Linux内核机制的深刻理解。 书中的核心知识点可能包括但不限于: 1. Linux内核概述:介绍了Linux内核的基本概念、内核版本和相关术语。让读者对内核有一个宏观的认识。 2. 内核模块:详细讲述了内核模块的概念、编写和加载方法。模块化是Linux内核设计的一个重要特点,它允许内核动态地扩展和更新功能。 3. 内存管理:解析了Linux内核中内存管理的机制,包括物理内存和虚拟内存的概念,以及相关数据结构的设计。 4. 进程调度:描述了Linux内核如何管理进程和线程,包括进程状态、调度策略和实现调度算法的核心代码分析。 5. 文件系统:深入分析Linux内核对文件系统的支持,解释了虚拟文件系统(VFS)的概念,以及具体的文件系统实现。 6. 网络通信:讲解了Linux内核网络层的设计和实现,包括网络协议栈的架构,以及数据包的处理流程。 7. 设备驱动:介绍了如何编写和管理Linux设备驱动程序,包括驱动程序与内核的接口以及设备的注册和注销机制。 8. 系统调用:解释了系统调用的概念和在Linux内核中的实现,包括系统调用的分派机制和常见的系统调用接口。 9. 内核同步机制:分析了内核中用于保证数据一致性和并发控制的同步机制,如互斥锁、信号量、自旋锁等。 10. 内核调试和性能分析:提供了关于如何使用工具对Linux内核进行调试和性能分析的方法和技巧。 除了上述核心知识点,本书可能还包含了对特定版本Linux内核的详细分析,帮助读者跟踪内核的最新发展和更新。 综上所述,"Linux_code_read.rar_linux"压缩包提供了一本适合初学者阅读的Linux内核学习资源,通过阅读本书,结合源代码分析,学习者将能够逐步构建起对Linux内核的深入理解,为后续的系统开发和优化打下坚实的基础。

优化sql:SELECT we.organization_id ,we.wip_entity_id ,case when wl.line_id is null then we.wip_entity_name else '' end wip_entity_name ,we.primary_item_id ,mtt.transaction_type_name ,mmt.transaction_date ,bd.department_code ,mmt.inventory_item_id ,mmt.subinventory_code ,mta.reference_account ,br.resource_code ,lu2.meaning as line_type_name ,mta.base_transaction_value ,mta.cost_element_id ,flv.meaning as cost_element ,wdj.class_code job_type_code ,ml.meaning job_type_name FROM (select * from gerp.mtl_material_transactions where substr(transaction_date,1,7) >= '2023-06' and transaction_source_type_id = 5) mmt inner join gerp.wip_entities we on mmt.organization_id = we.organization_id inner join gerp.mtl_transaction_accounts mta on mta.transaction_source_id = we.wip_entity_id and mta.transaction_id = mmt.transaction_id and mta.transaction_source_type_id = 5 inner join gerp.mtl_transaction_types mtt on mtt.transaction_type_id = mmt.transaction_type_id inner join mfg_lookups lu2 on lu2.lookup_code = mta.accounting_line_type and lu2.lookup_type = 'CST_ACCOUNTING_LINE_TYPE' inner join gerp.mtl_system_items_b msi on msi.inventory_item_id = mmt.inventory_item_id and msi.organization_id = mta.organization_id left join gerp.bom_departments bd on bd.department_id = mmt.department_id left join gerp.bom_resources br on br.resource_id = mta.resource_id left join gerp.wip_lines wl on wl.line_id = mmt.repetitive_line_id left join gerp.wip_discrete_jobs wdj on wdj.wip_entity_id = mta.transaction_source_id left join gerp.fnd_lookup_values_vl flv on cast(mta.cost_element_id as string) = flv.lookup_code and flv.lookup_type = 'CST_COST_CODE_TYPE' left join mfg_lookups ml on ml.lookup_code = wdj.job_type and ml.lookup_type = 'WIP_DISCRETE_JOB' 。其中mmt,we,mta,msi,wdj数据量很大

2023-06-10 上传

优化这个sql SELECT count( 1 ) FROM ( SELECT B.ID, B.PURCHASE_REQUEST_ID, B.MATERIAL_ID, B.MATERIAL_CODE, B.MATERIAL_NAME, B.STANDARD, B.MODEL_ID, B.BILL_ROW_ID, B.BILL_NO, BILL_NAME, B.MODEL_CODE, B.MODEL_NAME, B.PARENT_MODEL_ID, B.PARENT_MODEL_CODE, B.PARENT_MODEL_NAME, B.UNIT_CODE, B.UNIT_NAME, B.PURCHASE_TYPE_CODE, CAST( NVL( B.APPLY_NUM, 0 ) AS NUMBER ( 24, 10 ) ) AS APPLY_NUM, CAST( NVL( B.DEAL_NUM, 0 ) AS NUMBER ( 24, 10 ) ) AS DEAL_NUM, CAST( NVL( B.RETURN_NUM, 0 ) AS NUMBER ( 24, 10 ) ) AS RETURN_NUM, B.DEAL_USER_ID, B.DEAL_USER_NAME, CAST( NVL( B.PRICE, 0 ) AS NUMBER ( 24, 10 ) ) AS PRICE, CAST( NVL( B.AMOUNT, 0 ) AS NUMBER ( 24, 10 ) ) AMOUNT, B.IMPLEMENT_CODE, B.IMPLEMENT_NAME, B.IMPLEMENT_INVEST_AMOUNT, B.PURCHASE_MANAGER_ID, B.PURCHASE_MANAGER_NAME, B.PROVIDER_ID, B.PROVIDER_NAME, B.REMARK, B.DELIVER_AREA, B.DELIVER_ADDRESS, B.RECEIVE_PEOPLE, B.RECEIVE_PEOPLE_PHONE, B.ITEM_STATUS, B.COST_CENTER, B.COST_BUDGET_CODE, B.COST_IMPLEMENT_NAME, B.FRAME_CONT_ID, B.FRAME_CONT_CODE, B.FRAME_CONT_NAME, B.DETAIL_CONFIG, B.PURCHASE_CATEGORY_CODE, B.INVOICE_TITLE_CODE, B.INVOICE_SEND_ADDRRSS, B.MATERIAL_REQUEST_ITEM_ID, B.YEAR, B.DELETE_FLAG, B.PROVINCE_CODE, B.REASON, B.PARENT_ITEM_ID, B.FRAME_CONT_ITEM_ID, B.SUB_MATERIAL_REQUEST_ID, B.SUB_MATERIAL_REQUEST_CODE, B.MATERIAL_URL, B.RECOMMEND_PROVIDER_NAMES, C.PURCHASE_REQUEST_CODE, C.PURCHASE_REQUEST_NAME, C.APPLY_TYPE_CODE, C.CREATOR_NAME, C.APPLY_TELEPHONE, C.COMPANY_NAME, C.DEPT_NAME, B.CREATE_TIME, TO_CHAR( B.CREATE_TIME, 'YYYY-MM-DD' ) CREATE_TIME_STR, C.ARRIVE_TIME, C.IS_TO_END, C.MONEY_WAY_CODE, C.OWN, C.APPLY_CATEGORY_CODE, C.manu_Type, C.BILL_ID, MMD.MATERIAL_TYPE_CODE, B.BRANCH_COMPANY_DEAL_USER_ID, B.BRANCH_COMPANY_DEAL_USER_NAME, ( SELECT ORG_NAME FROM ORGANIZATIONS WHERE DELETE_FLAG = '0' AND ORG_CODE = ( SELECT PARENT_COMPANY_NO FROM ORGANIZATIONS WHERE ID = B.MATERIAL_DEPT_ID )) AS MATERIAL_COMPANY_NAME, B.ORIGINAL, B.PROVIDER_PRODUCT_MODEL, B.PROVIDER_PRODUCT_NAME, B.PRODUCT_DESC, B.Back_Flag, CASE WHEN MMD.material_type_code = 'WZ' THEN '1' WHEN MMD.material_type_code = 'FW' THEN '2' ELSE '3' END apply_category_code_item, NVL( C.IS_CARDSYSTEM_REQUEST, '0' ) IS_CARDSYSTEM_REQUEST, B.APPLY_GROUP_AUTHORITES, B.SCIENTIFIC_RESEARCH_ID, B.SCIENTIFIC_RESEARCH_CODE, B.SCIENTIFIC_RESEARCH_NAME, B.PREQUALFY_CODE, nvl( C.IS_QUICK, '0' ) AS IS_QUICK, C.PURCHASE_WAY_CODE, C.PURCHASE_TYPE_CODE PURCHASE_TYPE_CODE_P, C.ORIGINAL_TYPE, C.PURCHASE_REQUEST_BILLS_TYPE, B.IS_FRAME_CONT_MONAD FROM PURCHASE_REQUEST_ITEM B LEFT JOIN PURCHASE_REQUEST C ON B.PURCHASE_REQUEST_ID = C.ID LEFT JOIN MATERIAL_DATA MMD ON MMD.ID = B.MATERIAL_ID AND MMD.DELETE_FLAG = '0' WHERE B.delete_flag = '0' AND B.Item_Status IN ( 1 ) AND NOT EXISTS ( SELECT * FROM purchase_request_item_log pril WHERE B.id = pril.purchase_request_item_id AND pril.lock_status = '1' AND pril.delete_flag = '0' ) AND ( ( c.apply_type_code NOT IN ( '20', '41', '3' ) AND nvl( B.Apply_Num, 0 ) > nvl( B.Deal_Num, 0 )) OR c.apply_type_code IN ( '20', '41', '3' ) ) AND B.Deal_User_Id =: 1 AND C.MONEY_WAY_CODE =: 2 AND C.APPLY_TYPE_CODE =: 3 AND C.PAY_OUT_TYPE_CODE =: 4 AND C.APPLY_CATEGORY_CODE =: 5 AND NVL( C.IS_CARDSYSTEM_REQUEST, '0' ) = : 6 AND NOT EXISTS ( SELECT * FROM purchase_request_item p left join material_province mp ON p.material_id = mp.material_id WHERE p.delete_flag = 0 AND mp.delete_flag = 0 AND mp.material_status = 03 AND mp.org_code = p.province_code AND p.id = B.id ) ORDER BY C.ID, B.ID ASC)

2023-06-08 上传